VS: Fix CSharp flag selection when linking to a static C++ library

When a CSharp target links to a static C++ library, CMake will compute
the link language as C++ instead of CSharp.  That may be incorrect and
needs further investigation, but it does not affect how VS drives C#
linking.  However, it does break our flag language selection logic
and causes C++ flags to be used for CSharp.  In particular, this
drops the `-platform:x86` flag on 32-bit builds.

Fix this by always selecting the CSharp flags when generating a
`.csproj` project type.

Issue: #18239

1 files changed, 5 insertions, 3 deletions

diff --git a/Source/cmVisualStudio10TargetGenerator.cxx b/Source/cmVisualStudio10TargetGenerator.cxx
index f472d8a..b8b04ae 100644
--- a/Source/cmVisualStudio10TargetGenerator.cxx
+++ b/Source/cmVisualStudio10TargetGenerator.cxx
@@ -2413,10 +2413,12 @@ bool cmVisualStudio10TargetGenerator::ComputeClOptions(
   }
 
   // Choose a language whose flags to use for ClCompile.
-  static const char* clLangs[] = { "CXX", "C", "Fortran", "CSharp" };
+  static const char* clLangs[] = { "CXX", "C", "Fortran" };
   std::string langForClCompile;
-  if (std::find(cm::cbegin(clLangs), cm::cend(clLangs), linkLanguage) !=
-      cm::cend(clLangs)) {
+  if (this->ProjectType == csproj) {
+    langForClCompile = "CSharp";
+  } else if (std::find(cm::cbegin(clLangs), cm::cend(clLangs), linkLanguage) !=
+             cm::cend(clLangs)) {
     langForClCompile = linkLanguage;
   } else {
     std::set<std::string> languages;