Add test to show save-temps is broken for amdgcn target. (#161472)

In response to request here
#160935
by @jansvoboda11

Author: carlobertolli

clang/test/OpenMP/amdgcn_save_temps.c

@@ -0,0 +1,25 @@
+
+// REQUIRES: amdgpu-registered-target
+
+// XFAIL: *
+
+// RUN: %clang_cc1 -E -fopenmp -x c -triple amdgcn-amd-amdhsa -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd %s -o %t-openmp-amdgcn-amd-amdhsa-gfx90a.i
+// RUN: %clang_cc1 -fopenmp  -x c -triple x86_64-unknown-unknown -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd -emit-llvm-bc %s -o %t-x86_64-unknown-unknown.bc
+// RUN: %clang_cc1 -fopenmp -x c -triple amdgcn-amd-amdhsa -fopenmp-targets=amdgcn-amd-amdhsa -save-temps=cwd -emit-llvm -fopenmp-is-target-device -x cpp-output %t-openmp-amdgcn-amd-amdhsa-gfx90a.i -fopenmp-host-ir-file-path %t-x86_64-unknown-unknown.bc -o - | FileCheck %s
+// expected-no-diagnostics
+#ifndef HEADER
+#define HEADER
+
+#define N 1000
+
+int test_amdgcn_save_temps() {
+  int arr[N];
+#pragma omp target
+  for (int i = 0; i < N; i++) {
+    arr[i] = 1;
+  }
+  return arr[0];
+}
+#endif
+
+// CHECK: define {{[^@]+}}@{{__omp_offloading_[0-9a-z]+_[0-9a-z]+}}_test_amdgcn_save_temps