Tests: Add case for Xcode per-config per-source COMPILE_FLAGS diagnostic

Tests/RunCMake/XcodeProject/PerConfigPerSourceFlags-result.txt

+1

Tests/RunCMake/XcodeProject/PerConfigPerSourceFlags-stderr.txt

+^CMake Error in CMakeLists.txt:
+  Xcode does not support per-config per-source COMPILE_FLAGS:
+
+    \$<\$<CONFIG:Debug>:-DMYDEBUG>
+
+  specified for source:
+
+    .*/Tests/RunCMake/XcodeProject/main.c$

Tests/RunCMake/XcodeProject/PerConfigPerSourceFlags.cmake

+enable_language(C)
+add_executable(main main.c)
+set_property(SOURCE main.c PROPERTY COMPILE_FLAGS "$<$<CONFIG:Debug>:-DMYDEBUG>")

Tests/RunCMake/XcodeProject/RunCMakeTest.cmake

@@ -13,6 +13,8 @@ if (NOT XCODE_VERSION VERSION_LESS 6)
   run_cmake(XcodePlatformFrameworks)
 endif()
 
+run_cmake(PerConfigPerSourceFlags)
+
 # Use a single build tree for a few tests without cleaning.
 
 if(NOT XCODE_VERSION VERSION_LESS 5)