fetchDependencies build external libraries in parallel by platform.

Log ext lib build steps to provide user feedback.
Add package_ext_libs_finish.sh script to separate packaging
libraries from building them, to avoid build database conflicts.
Travis only build macOS ext libs.

.travis.yml

@@ -6,7 +6,7 @@ osx_image: xcode11.5
 
 # Build dependencies with verbose logging to avoid Travis timing out.
 install:
-  - ./fetchDependencies -v
+  - ./fetchDependencies -v --macos
 
 script:
   - xcodebuild -project MoltenVKPackaging.xcodeproj -scheme "MoltenVK Package"

Docs/Whats_New.md

@@ -21,6 +21,7 @@ Released TBD
 - Add support for extensions:
 	- VK_KHR_sampler_ycbcr_conversion
 	- VK_EXT_robustness2
+- `fetchDependencies` script supports platform build selection. 
 - Fix issue where mapped host-coherent device memory not updated from image contents on *macOS*.
 - Remove use of `@available()` directive as it was causing issues in some build environments.
 - Refactor **MoltenVK** *Xcode* build architectures.

ExternalDependencies.xcodeproj/project.pbxproj

@@ -55,11 +55,12 @@
 			isa = PBXAggregateTarget;
 			buildConfigurationList = A972A7F521CEC81B0013AB25 /* Build configuration list for PBXAggregateTarget "ExternalDependencies" */;
 			buildPhases = (
+				A9FC5F8B249DB48D003CB086 /* Package Finish */,
 			);
 			dependencies = (
+				A972A7F921CEC8500013AB25 /* PBXTargetDependency */,
 				A972A7FB21CEC8540013AB25 /* PBXTargetDependency */,
 				2FEA0CF82490344F00EEF3AD /* PBXTargetDependency */,
-				A972A7F921CEC8500013AB25 /* PBXTargetDependency */,
 			);
 			name = ExternalDependencies;
 			productName = "ExternalLibraries-macOS";
@@ -2185,6 +2186,7 @@
 		A9765DF02485758500FDD115 /* decoration.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = decoration.h; sourceTree = "<group>"; };
 		A9C2104521D14FD7006BA2D3 /* fetchDependencies */ = {isa = PBXFileReference; lastKnownFileType = text; path = fetchDependencies; sourceTree = "<group>"; };
 		A9C2104721D15843006BA2D3 /* ExternalRevisions */ = {isa = PBXFileReference; lastKnownFileType = folder; path = ExternalRevisions; sourceTree = "<group>"; };
+		A9FC5F7F249DA96D003CB086 /* package_ext_libs_finish.sh */ = {isa = PBXFileReference; lastKnownFileType = text.script.sh; path = package_ext_libs_finish.sh; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXGroup section */
@@ -2391,6 +2393,7 @@
 				A932E9DF249BC44D00D64150 /* create_fat_ext_libs.sh */,
 				A932E9C5249A743B00D64150 /* create_fat_lib_func.sh */,
 				A91BF011235F9C510039B7DE /* gen_spirv_cross_rev_hdr.sh */,
+				A9FC5F7F249DA96D003CB086 /* package_ext_libs_finish.sh */,
 				A9679AAE21D269D900856BF7 /* package_ext_libs.sh */,
 				A9415EF624366B0E00566F16 /* packagePregenSpirvToolsHeaders */,
 			);
@@ -4069,6 +4072,24 @@
 			shellPath = /bin/sh;
 			shellScript = "export MVK_OS=\"tvOS\"\nexport MVK_OS_PROD_EXTN=\"appletvos\"\nexport MVK_SIM_PROD_EXTN=\"appletvsimulator\"\n\n. \"${SRCROOT}/Scripts/create_fat_ext_libs.sh\"\n";
 		};
+		A9FC5F8B249DB48D003CB086 /* Package Finish */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			name = "Package Finish";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = ". \"${SRCROOT}/Scripts/package_ext_libs_finish.sh\"\n";
+		};
 /* End PBXShellScriptBuildPhase section */
 
 /* Begin PBXSourcesBuildPhase section */

Scripts/package_ext_libs.sh

@@ -9,10 +9,3 @@ rm -rf "${MVK_EXT_LIB_DST_OS_PATH}"
 mkdir -p "${MVK_EXT_LIB_DST_OS_PATH}"
 
 cp -a "${MVK_BUILT_PROD_PATH}/"*.a "${MVK_EXT_LIB_DST_OS_PATH}"
-
-# Assign symlink to Latest
-ln -sfn "${CONFIGURATION}" "${MVK_EXT_LIB_DST_PATH}/Latest"
-
-# Clean MoltenVK to ensure the next MoltenVK build will use the latest external library versions.
-make --quiet clean
-

Scripts/package_ext_libs_finish.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -e
+
+export MVK_EXT_LIB_DST_PATH="${PROJECT_DIR}/External/build/"
+
+# Assign symlink to Latest
+ln -sfn "${CONFIGURATION}" "${MVK_EXT_LIB_DST_PATH}/Latest"
+
+# Clean MoltenVK to ensure the next MoltenVK build will use the latest external library versions.
+make --quiet clean
+

fetchDependencies

@@ -36,6 +36,9 @@
 #              Build the external libraries in Debug mode, which may be useful when debugging
 #              and tracing calls into those libraries.
 #
+#      --no-parallel-build
+#              Build the external libraries serially instead of in parallel using background processes.
+#
 #      --glslang-root path
 #              "path" specifies a directory path to a KhronosGroup/glslang repository.
 #              This repository does need to be built and the build directory must be in the
@@ -74,6 +77,7 @@ BLD_MACOS=""
 BLD_SPECIFIED=""
 XC_CONFIG="Release"
 XC_BUILD_VERBOSITY="-quiet"
+XC_USE_BCKGND="Y"
 V_HEADERS_ROOT=""
 SPIRV_CROSS_ROOT=""
 GLSLANG_ROOT=""
@@ -121,6 +125,10 @@ while (( "$#" )); do
          XC_CONFIG="Debug"
          shift 1
          ;;
+       --no-parallel-build)
+         XC_USE_BCKGND=""
+         shift 1
+         ;;
        -v)
          XC_BUILD_VERBOSITY=""
          shift 1
@@ -357,57 +365,102 @@ cd -  > /dev/null
 cd ..
 
 
-# -------------- Build MoltenVK dependencies -----------------
-echo
-echo ========== Building dependency libraries quietly. Please be patient on first build. ==========
+# -------------- Build MoltenVK external library dependencies -----------------
 echo
+echo ========== Started building dependency libraries at `date +"%r"` ==========
+echo Please be patient on first build
+
+# Build an Xcode scheme for an OS and platform
+# 1 - OS
+# 2 - platform
+function build_impl() {
+	XC_OS=${1}
+	XC_PLTFM=${2}
+
+	XC_SCHEME="${EXT_DEPS}-${XC_OS}"
+	XC_LCL_DD_PATH="${XC_DD_PATH}/Intermediates/${XC_OS}"
+	XC_DEST="generic/platform=${XC_PLTFM}"
 
-# Build an Xcode scheme
-function build() {
 	echo Building external libraries for ${XC_PLTFM}
+
 	xcodebuild 										\
 		-project "${XC_PROJ}"						\
 		-scheme "${XC_SCHEME}"						\
-		-destination "generic/platform=${XC_PLTFM}"	\
+		-destination "${XC_DEST}"					\
 		-configuration "${XC_CONFIG}"				\
-		-derivedDataPath "${XC_DD_PATH}"			\
+		-derivedDataPath "${XC_LCL_DD_PATH}"		\
 		${XC_BUILD_VERBOSITY}						\
 		build
+
+	echo Completed building external libraries for ${XC_PLTFM}
+}
+
+# Select whether or not to run the build in parallel.
+# 1 - OS
+# 2 - platform
+function build() {
+	if [ "$XC_USE_BCKGND" != "" ]; then
+		build_impl ${1} ${2} &
+	else
+		build_impl ${1} ${2}
+	fi
+}
+
+# Build a fat library for the OS containing code for the OS and its Simulator
+# Builds serially to ensure both are built
+# 1 - OS
+function build_fat_impl() {
+	XC_OS=${1}
+
+	build_impl ${XC_OS} ${XC_OS}
+	build_impl ${XC_OS} "${XC_OS} Simulator"
+}
+
+# Select whether or not to run the build in parallel.
+# 1 - OS
+function build_fat() {
+	if [ "$XC_USE_BCKGND" != "" ]; then
+		build_fat_impl ${1} &
+	else
+		build_fat_impl ${1}
+	fi
 }
 
 EXT_DEPS=ExternalDependencies
 XC_PROJ="${EXT_DEPS}.xcodeproj"
 XC_DD_PATH="${EXT_DIR}/build"
 
-if [ "$BLD_IOS" != "" ]; then
-	XC_SCHEME="${EXT_DEPS}-iOS"
-	XC_PLTFM="iOS"
-	build
+# Structure build tasks by platform so they can be built in parallel per platform.
+# Content for each platform must be built in series to avoid
+trap "exit" INT TERM ERR
+trap "kill 0" EXIT
+
+if [ "$BLD_MACOS" != "" ]; then
+	build "macOS" "macOS"
 fi
 
-if [ "$BLD_IOS_SIM" != "" ]; then
-	XC_SCHEME="${EXT_DEPS}-iOS"
-	XC_PLTFM="iOS Simulator"
-	build
+if [ "$BLD_IOS" != "" ]; then
+	if [ "$BLD_IOS_SIM" != "" ]; then
+		build_fat "iOS"
+	else
+		build "iOS" "iOS"
+	fi
 fi
 
 if [ "$BLD_TVOS" != "" ]; then
-	XC_SCHEME="${EXT_DEPS}-tvOS"
-	XC_PLTFM="tvOS"
-	build
+	if [ "$BLD_TVOS_SIM" != "" ]; then
+		build_fat "tvOS"
+	else
+		build "tvOS" "tvOS"
+	fi
 fi
 
-if [ "$BLD_TVOS_SIM" != "" ]; then
-	XC_SCHEME="${EXT_DEPS}-tvOS"
-	XC_PLTFM="tvOS Simulator"
-	build
-fi
+# Wait for any background process (if selected) to finish
+wait
 
-if [ "$BLD_MACOS" != "" ]; then
-	XC_SCHEME="${EXT_DEPS}-macOS"
-	XC_PLTFM="macOS"
-	build
-fi
-
-echo ========== Done! ==========
+# Update latest symlink and clean MoltenVK for rebuild
+PROJECT_DIR="."
+CONFIGURATION=${XC_CONFIG}
+. "./Scripts/package_ext_libs_finish.sh"
 
+echo ========== Finished at `date +"%r"` ==========