[libclc] [llvm] [libclc] Refactor build system to allow in-tree builds (PR #87622)

[Fraser Cormack via cfe-commits]

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@@ -358,3 +399,7 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
     endif()
   endforeach( d )
 endforeach( t )
+
+if( NOT LIBCLC_STANDALONE_BUILD )
+  add_subdirectory( test )
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frasercrmck wrote:

Ach yeah sorry, I have another path locally which adds some LIT tests - this should be in that one. I'll remove it for now, and we can maybe decide whether or not to add LIT testing to this PR or not.

https://github.com/llvm/llvm-project/pull/87622