Change how AppVeyor build is invoked

appveyor.yml

@@ -4,5 +4,6 @@ environment:
   myget_api_key:
     secure: 0xJoYAtR6psXCRvk1qm5czDObkeRjHKPjfe5gIExXVFPwA0VVODYv/hBZYUtz2F3
 build_script:
-  - ps: .\build.ps1 appveyorbuild
+  - cmd: .\build.cmd appveyorbuild
+  - sh: ./build.cmd appveyorbuild
 test: off

build.bat

@@ -1 +0,0 @@
-powershell -ExecutionPolicy Bypass -NoProfile -File .\build.ps1 %* -configuration Release 

build.cmd

@@ -0,0 +1,7 @@
+:; set -eo pipefail
+:; SCRIPT_DIR=$(cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd)
+:; ${SCRIPT_DIR}/build.sh "$@"
+:; exit $?
+
+@ECHO OFF
+powershell -ExecutionPolicy ByPass -NoProfile "%~dp0build.ps1" %*