[libc][NFC] More verbose warning message on missing utilities

Summary:
The GPU needs both the loader utility and the architecture to be present
to run tests. This simply makes it easier to detect which is missing in
case of problems.

Author: jhuber6

libc/test/CMakeLists.txt

@@ -8,10 +8,14 @@ add_custom_target(libc-long-running-tests)
 
 add_subdirectory(UnitTest)
 
-if(LIBC_TARGET_OS_IS_GPU AND
-   (NOT TARGET libc.utils.gpu.loader OR LIBC_GPU_TESTS_DISABLED))
-  message(WARNING "Cannot build libc GPU tests, missing loader or architecture")
-  return()
+if(LIBC_TARGET_OS_IS_GPU)
+  if(NOT TARGET libc.utils.gpu.loader)
+    message(WARNING "Cannot build libc GPU tests, missing loader.")
+    return()
+  elseif(LIBC_GPU_TESTS_DISABLED)
+    message(WARNING "Cannot build libc GPU tests, missing target architecture.")
+    return()
+  endif()
 endif()
 
 add_subdirectory(include)