VS: Use StdOutEncoding for VS 16.7 Preview 3 and above

VS 16.6 added a `StdOutEncoding` setting for custom commands to tell
MSBuild that the output is encoded as UTF-8.  In commit bc877a7e94 (Add
support to indicate UTF-8 custom command pipe output encoding,
2020-04-08) CMake learned to add the setting in anticipation of the VS
16.6 release.  However, when 16.6 was released it had a bug in the
implementation of custom tasks with StdOutEncoding enabled that was
exposed by our test suite.  In commit 5058fb5401 (VS: Drop
StdOutEncoding with VS 16.6 pending investigation, 2020-05-29) we
disabled the setting pending investigation.

The problem is fixed in VS 16.7 Preview 3, so restore use of the
setting when a VS instance of at least that version is detected.

Fixes: #20769

1 files changed, 15 insertions, 0 deletions

diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.cxx b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
index d44433b..605dc8b 100644
--- a/Source/cmGlobalVisualStudioVersionedGenerator.cxx
+++ b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
@@ -393,6 +393,21 @@ bool cmGlobalVisualStudioVersionedGenerator::IsDefaultToolset(
   return false;
 }
 
+bool cmGlobalVisualStudioVersionedGenerator::IsStdOutEncodingSupported() const
+{
+  // Supported from Visual Studio 16.7 Preview 3.
+  if (this->Version > cmGlobalVisualStudioGenerator::VSVersion::VS16) {
+    return true;
+  }
+  if (this->Version < cmGlobalVisualStudioGenerator::VSVersion::VS16) {
+    return false;
+  }
+  unsigned long long const vsInstanceVersion16_7_P2 = 4503631666610212;
+  unsigned long long vsInstanceVersion;
+  return (this->GetVSInstanceVersion(vsInstanceVersion) &&
+          vsInstanceVersion > vsInstanceVersion16_7_P2);
+}
+
 std::string cmGlobalVisualStudioVersionedGenerator::GetAuxiliaryToolset() const
 {
   const char* version = this->GetPlatformToolsetVersion();