[compiler-rt][tests] cpu_model_test.c test fails to compile if X86 is not clang's default target

[iid_iunknown]

Summary

test/builtins/Unit/cpu_model_test.c tests the X86 specific builtin __builtin_cpu_supports.
It fails if the clang's default target is not X86.

The proposed patch adds an additional requirement for the X86 target to the test, making lit ignore the test if the target is different.

[asbirlea]

LGTM

[iid_iunknown]

Thank you for the review, Alina.

test/builtins/Unit/cpu_model_test.c

 //===-- cpu_model_test.c - Test __builtin_cpu_supports -------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file tests __builtin_cpu_supports for the compiler_rt library.
 //
 //===----------------------------------------------------------------------===//
 
+// REQUIRES: x86-target-arch
+
 int main (void) {
   if(__builtin_cpu_supports("avx2"))
     return 4;
   else
     return 3;
 }