Fix aarch64-ptrauth.c to avoid writing to cwd which might not be writeable

Some of the tests seem to test beyond the driver (& check a warning
coming from the frontend) and should probably be split into separate
tests.

Author: dwblaikie

clang/test/Driver/aarch64-ptrauth.c

@@ -49,14 +49,14 @@
 // ERR1-NEXT: error: unsupported option '-fptrauth-init-fini' for target '{{.*}}'
 
 //// Only support PAuth ABI for Linux as for now.
-// RUN: not %clang -c --target=aarch64-unknown -mabi=pauthtest %s 2>&1 | FileCheck %s --check-prefix=ERR2
-// RUN: not %clang -c --target=aarch64-unknown-pauthtest       %s 2>&1 | FileCheck %s --check-prefix=ERR2
+// RUN: not %clang -o /dev/null -c --target=aarch64-unknown -mabi=pauthtest %s 2>&1 | FileCheck %s --check-prefix=ERR2
+// RUN: not %clang -o /dev/null -c --target=aarch64-unknown-pauthtest       %s 2>&1 | FileCheck %s --check-prefix=ERR2
 // ERR2: error: ABI 'pauthtest' is not supported for 'aarch64-unknown-unknown-pauthtest'
 
 //// PAuth ABI is encoded as environment part of the triple, so don't allow to explicitly set other environments.
-// RUN: not %clang -c --target=aarch64-linux-gnu -mabi=pauthtest %s 2>&1 | FileCheck %s --check-prefix=ERR3
+// RUN: not %clang -### -c --target=aarch64-linux-gnu -mabi=pauthtest %s 2>&1 | FileCheck %s --check-prefix=ERR3
 // ERR3: error: unsupported option '-mabi=pauthtest' for target 'aarch64-unknown-linux-gnu'
-// RUN: %clang -c --target=aarch64-linux-pauthtest -mabi=pauthtest %s
+// RUN: %clang -### -c --target=aarch64-linux-pauthtest -mabi=pauthtest %s
 
 //// The only branch protection option compatible with PAuthABI is BTI.
 // RUN: not %clang -### -c --target=aarch64-linux -mabi=pauthtest -mbranch-protection=pac-ret %s 2>&1 | \