[libclc] [llvm] [libclc] Support LLVM_ENABLE_RUNTIMES when building (PR #141574)

[Romaric Jodin via llvm-commits]

================
@@ -204,6 +204,13 @@ if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
   endif ()
 endif ()
 
+if ("libclc" IN_LIST LLVM_ENABLE_PROJECTS)
+  message(WARNING "Using LLVM_ENABLE_PROJECTS=libclc is deprecated now, and will "
+    "become a fatal error in the LLVM 21 release.  Please use "
+    "-DLLVM_ENABLE_RUNTIMES=libclc or see the instructions at "
+    "https://libclc.llvm.org/ for building the runtimes.")
----------------
rjodinchr wrote:

So, that's a difference with the actual setup, where it is possible to do that.

What about all the dependency between libclc and clang, would that still be taken care of seamlessly? 

https://github.com/llvm/llvm-project/pull/141574