[llvm] Fix warnings while building llvm against emscripten for web assembly (PR #118262)

[Anutosh Bhat via llvm-commits]

================
@@ -635,6 +635,11 @@ function(llvm_add_library name)
     set(ARG_STATIC)
   endif()
 
+  if(EMSCRIPTEN)
----------------
anutosh491 wrote:

Done.

https://github.com/llvm/llvm-project/pull/118262