NMake: Use UTF-8 BOM in response files only with MSVC tooling

Since commit f3f57cc4ed (NMake: Use UTF-8 with BOM if supported by
nmake, 2021-04-22, v3.21.0-rc1~217^2), we add a BOM to response files
to tell MSVC tooling that they are encoded as UTF-8.  However, the
"NMake Makefiles" generator may also be used with non-MSVC toolchains
that do not understand the BOM.  Update the response file encoding
selection heuristic to add the BOM only with MSVC tooling.

Fixes: #23143

Source/cmMakefileTargetGenerator.cxx

@@ -2053,6 +2053,11 @@ std::string cmMakefileTargetGenerator::CreateResponseFile(
   // For now, use the makefile encoding as a heuristic.
   codecvt::Encoding responseEncoding =
     this->GlobalGenerator->GetMakefileEncoding();
+  // Non-MSVC tooling may not understand a BOM.
+  if (responseEncoding == codecvt::UTF8_WITH_BOM &&
+      !this->Makefile->IsOn("MSVC")) {
+    responseEncoding = codecvt::UTF8;
+  }
 
   // Create the response file.
   std::string responseFileNameFull =