[SYCL][NFC] Update libsycl file print test (#6812)

The test which verifies the proper -print-file-name=libsycl.so output
was to dependent on external existence of the library itself. Update the
test so we use an internal location check.

Author: mdtoguchi

clang/test/Driver/Inputs/SYCL/lib/libsycl.so

@@ -1,6 +1,6 @@
 // UNSUPPORTED: system-windows
 
 // -print-file-name=libsycl.so
-// RUN: %clangxx -print-file-name=libsycl.so 2>&1 | FileCheck %s --check-prefix=PRINT_LIBSYCL
-// RUN: %clangxx -fsycl -print-file-name=libsycl.so 2>&1 | FileCheck %s --check-prefix=PRINT_LIBSYCL
+// RUN: %clangxx -print-file-name=libsycl.so --sysroot=%S/Inputs/SYCL 2>&1 | FileCheck %s --check-prefix=PRINT_LIBSYCL
+// RUN: %clangxx -fsycl -print-file-name=libsycl.so --sysroot=%S/Inputs/SYCL 2>&1 | FileCheck %s --check-prefix=PRINT_LIBSYCL
 // PRINT_LIBSYCL: {{.*}}lib{{(\\\\|/)}}libsycl.so