[clang][Headers][lit] Fix test arm-acle-no-direct-include.c on Mac (#158677)

See [here](#144172 (comment)), need to add `--` to filename parsing on Mac because the path starts with `/U` which `clang-cl` treats as the flag `/U`. Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

Author: sarnex

clang/test/Headers/arm-acle-no-direct-include.c

@@ -1,4 +1,4 @@
-// RUN: %clang_cl --target=aarch64-windows-msvc -Xclang -verify /E -U__STDC_HOSTED__ -Wno-builtin-macro-redefined %s 2>&1 | FileCheck %s
+// RUN: %clang_cl --target=aarch64-windows-msvc -Xclang -verify /E -U__STDC_HOSTED__ -Wno-builtin-macro-redefined -- %s 2>&1 | FileCheck %s
 
 // expected-no-diagnostics