specify clang --target to fix breakage on AIX (#114127)

`-fprofile-sample-use` is not supported on AIX, which caused a CI
failure.

Author: wlei-llvm

clang/test/CodeGen/pgo-cold-function-coverage.c

@@ -1,7 +1,7 @@
 // Test -fprofile-generate-cold-function-coverage 
 
 // RUN: rm -rf %t && split-file %s %t
-// RUN: %clang -O2 -fprofile-generate-cold-function-coverage=/xxx/yyy/ -fprofile-sample-accurate -fprofile-sample-use=%t/pgo-cold-func.prof  -S -emit-llvm -o - %t/pgo-cold-func.c | FileCheck %s
+// RUN: %clang --target=x86_64 -O2 -fprofile-generate-cold-function-coverage=/xxx/yyy/ -fprofile-sample-accurate -fprofile-sample-use=%t/pgo-cold-func.prof  -S -emit-llvm -o - %t/pgo-cold-func.c | FileCheck %s
 
 // CHECK: @__llvm_profile_filename = {{.*}} c"/xxx/yyy/default_%m.profraw\00"