VS: Fix compilation of single source with PCH in Unity Build

Sources that are part of a unity build are normally not compiled
individually.  However, the VS IDE allows a single source to be
compiled.  This can also be achieved on the command line:

    msbuild my.vcxproj ... -t:ClCompile -p:SelectedFiles=<src>

where `<src>` is the path in the vcxproj `ClCompile` entry.

In a target with precompiled headers, the source needs PCH settings to
support individual compilation even if the normal unity build does not.

Source/cmVisualStudio10TargetGenerator.cxx

@@ -2337,7 +2337,8 @@ void cmVisualStudio10TargetGenerator::WriteAllSources(Elem& e0)
         }
       }
 
-      if (si.Kind == cmGeneratorTarget::SourceKindObjectSource) {
+      if (si.Kind == cmGeneratorTarget::SourceKindObjectSource ||
+          si.Kind == cmGeneratorTarget::SourceKindUnityBatched) {
         this->OutputSourceSpecificFlags(e2, si.Source);
       }
       if (si.Source->GetPropertyAsBool("SKIP_PRECOMPILE_HEADERS")) {

Tests/RunCMake/VS10Project/RunCMakeTest.cmake

@@ -64,6 +64,21 @@ if (RunCMake_GENERATOR MATCHES "Visual Studio 1[0-4] 201[0-5]" OR
 else()
   run_cmake(UnityBuildNative)
   run_cmake(UnityBuildNativeGrouped)
+
+  function(run_UnityBuildPCH)
+    set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/UnityBuildPCH-build)
+    run_cmake(UnityBuildPCH)
+    set(RunCMake_TEST_NO_CLEAN 1)
+    set(vcxproj "${RunCMake_TEST_BINARY_DIR}/UnityBuildPCH.vcxproj")
+    if(EXISTS "${vcxproj}")
+      file(STRINGS ${vcxproj} vcxproj_strings REGEX "ClCompile[^\n]*UnityBuildPCH\\.c")
+    endif()
+    if(vcxproj_strings MATCHES "Include=\"([^\"]+)\"")
+      set(src "${CMAKE_MATCH_1}")
+      run_cmake_command(UnityBuildPCH-build ${CMAKE_COMMAND} --build . --config Debug --target UnityBuildPCH -- -t:ClCompile -p:SelectedFiles=${src})
+    endif()
+  endfunction()
+  run_UnityBuildPCH()
 endif()
 
 run_cmake(VsDotnetTargetFramework)

Tests/RunCMake/VS10Project/UnityBuildPCH-build-check.cmake

@@ -0,0 +1,10 @@
+set(obj "${RunCMake_TEST_BINARY_DIR}/UnityBuildPCH.dir/Debug/UnityBuildPCH.obj")
+if(NOT EXISTS "${obj}")
+  set(RunCMake_TEST_FAILED "Expected object file does not exist:\n  ${obj}")
+  return()
+endif()
+set(lib "${RunCMake_TEST_BINARY_DIR}/Debug/UnityBuildPCH.lib")
+if(EXISTS "${lib}")
+  set(RunCMake_TEST_FAILED "Unexpected library file exists:\n  ${lib}")
+  return()
+endif()

Tests/RunCMake/VS10Project/UnityBuildPCH.c

@@ -0,0 +1,4 @@
+int UnityBuildPCH(void)
+{
+  return 0;
+}

Tests/RunCMake/VS10Project/UnityBuildPCH.cmake

@@ -0,0 +1,4 @@
+enable_language(C)
+add_library(UnityBuildPCH STATIC UnityBuildPCH.c)
+target_precompile_headers(UnityBuildPCH PRIVATE UnityBuildPCH.h)
+set_property(TARGET UnityBuildPCH PROPERTY UNITY_BUILD ON)

Tests/RunCMake/VS10Project/UnityBuildPCH.h

@@ -0,0 +1 @@
+/* empty file */