emit_x64: Add missing <array> include

Commit 755adef62e504a8d616de9dda8937d2428a9471b introduced a helper
alias for std::array, eliminating the need to manually type out sizes
for them, however I forgot to add the include for <array>

src/backend_x64/emit_x64.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <array>
 #include <type_traits>
 #include <unordered_map>
 #include <unordered_set>