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, 8 insertions, 5 deletions

diff --git a/Help/manual/cmake-generator-expressions.7.rst b/Help/manual/cmake-generator-expressions.7.rst
index 186a9d2..da7df70 100644
--- a/Help/manual/cmake-generator-expressions.7.rst
+++ b/Help/manual/cmake-generator-expressions.7.rst
@@ -966,15 +966,18 @@ Compile Context
 
   .. versionadded:: 3.27
 
-  Content of ``...``, except while collecting :ref:`Target Usage Requirements`,
-  in which case it is the empty string.  This is intended for use in an
-  :prop_tgt:`INTERFACE_LINK_LIBRARIES` target property, typically populated
-  via the :command:`target_link_libraries` command, to specify private
-  compilation requirements without other usage requirements.
+  Content of ``...``, when collecting :ref:`Target Usage Requirements`,
+  otherwise it is the empty string.  This is intended for use in an
+  :prop_tgt:`INTERFACE_LINK_LIBRARIES` and :prop_tgt:`LINK_LIBRARIES` target
+  properties, typically populated via the :command:`target_link_libraries` command.
+  Provides compilation usage requirements without any linking requirements.
 
   Use cases include header-only usage where all usages are known to not have
   linking requirements (e.g., all-``inline`` or C++ template libraries).
 
+  Note that for proper evaluation of this expression requires policy :policy:`CMP0099`
+  to be set to `NEW`.
+
 Linker Language And ID
 ^^^^^^^^^^^^^^^^^^^^^^