cmGeneratorExpressionNode: implement `COMPILE_ONLY` genex

This generator expression is the inverse of `LINK_ONLY` and only coveys
usage requirements for the purposes of compilation. Its intended use is
to avoid needing to export targets that do not have link usage
requirements (e.g., header-only libraries) when used by another target.

See: #15415

1 files changed, 4 insertions, 0 deletions

diff --git a/Source/cmGeneratorExpressionDAGChecker.h b/Source/cmGeneratorExpressionDAGChecker.h
index df1e005..1919b01 100644
--- a/Source/cmGeneratorExpressionDAGChecker.h
+++ b/Source/cmGeneratorExpressionDAGChecker.h
@@ -90,6 +90,9 @@ struct cmGeneratorExpressionDAGChecker
   bool GetTransitivePropertiesOnly() const;
   void SetTransitivePropertiesOnly() { this->TransitivePropertiesOnly = true; }
 
+  bool GetTransitivePropertiesOnlyCMP0131() const;
+  void SetTransitivePropertiesOnlyCMP0131() { this->CMP0131 = true; }
+
   cmGeneratorExpressionDAGChecker const* Top() const;
   cmGeneratorTarget const* TopTarget() const;
 
@@ -105,4 +108,5 @@ private:
   const cmListFileBacktrace Backtrace;
   Result CheckResult;
   bool TransitivePropertiesOnly;
+  bool CMP0131;
 };