Merge topic 'xcode-12-legacy-deprecation' into release-3.18

36fc3a1e84 Xcode: Suppress legacy build system deprecation warning

Acked-by: Kitware Robot <[email protected]>
Merge-request: !5052

Source/cmGlobalXCodeGenerator.cxx

@@ -3483,6 +3483,8 @@ void cmGlobalXCodeGenerator::OutputXCodeWorkspaceSettings(
   if (this->XcodeVersion >= 100) {
     xout.Element("key", "BuildSystemType");
     xout.Element("string", "Original");
+    xout.Element("key", "DisableBuildSystemDeprecationWarning");
+    xout.Element("true");
   }
   if (hasGeneratedSchemes) {
     xout.Element("key",