[llvm] [OpenMP] Do not define '__assert_fail' if we have the GPU libc (PR #100409)

[Joseph Huber via llvm-commits]

================
@@ -26,10 +26,13 @@ using namespace ompx;
 extern "C" {
 void __assert_assume(bool condition) { __builtin_assume(condition); }
 
+#ifndef OMPTARGET_HAS_LIBC
----------------
jhuber6 wrote:

This is an existing macro, so if I wanted to use something else I'd need to rename it which would make the patch more complicated.

https://github.com/llvm/llvm-project/pull/100409