VS: Restore support for PCH in CXX but not C within once target

Fix logic from commit 9df1f33c9a (VisualStudio: move PCH rules to
projects when possible., 2020-10-15, v3.20.0-rc1~638^2) to explicitly
disable PCH on sources that should not use the target-wide PCH rules.

Fixes: #21827

1 files changed, 5 insertions, 1 deletions

diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index 50a456d..6a90675 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -2423,8 +2423,10 @@ void cmVisualStudio10TargetGenerator::OutputSourceSpecificFlags(
     const bool makePCH = (sf.GetFullPath() == pchSource);
     const bool useSharedPCH = !skipPCH && (lang == linkLanguage);
     const bool useDifferentLangPCH = !skipPCH && (lang != linkLanguage);
+    const bool useNoPCH = skipPCH && (lang != linkLanguage) &&
+      !this->GeneratorTarget->GetPchHeader(config, linkLanguage).empty();
     const bool needsPCHFlags =
-      (makePCH || useSharedPCH || useDifferentLangPCH);
+      (makePCH || useSharedPCH || useDifferentLangPCH || useNoPCH);
 
     // if we have flags or defines for this config then
     // use them
@@ -2471,6 +2473,8 @@ void cmVisualStudio10TargetGenerator::OutputSourceSpecificFlags(
         if (makePCH) {
           pchOptions =
             this->GeneratorTarget->GetPchCreateCompileOptions(config, lang);
+        } else if (useNoPCH) {
+          clOptions.AddFlag("PrecompiledHeader", "NotUsing");
         } else if (useSharedPCH) {
           std::string pchHeader =
             this->GeneratorTarget->GetPchHeader(config, lang);