[NFC] Add some tests to check for change in default header search dirs

Author: mdtoguchi

clang/test/Driver/sycl-device.cpp

@@ -6,7 +6,7 @@
 /// Check "-fsycl-is-device" is passed when compiling for device:
 // RUN:   %clang -### -fsycl-device-only %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-SYCL-DEV %s
-// CHECK-SYCL-DEV: "-fsycl-is-device"{{.*}} "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl"
+// CHECK-SYCL-DEV: "-fsycl-is-device"{{.*}} "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl" "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include"
 
 /// Check that "-Wno-sycl-strict" is set on compiler invocation with "-fsycl"
 /// or "-fsycl-device-only" or both:

clang/test/Driver/sycl-offload.c

@@ -922,3 +922,9 @@
 // CHK-POST-LINK-OPT-LEVEL-O3: sycl-post-link{{.*}} "-O3"
 // CHK-POST-LINK-OPT-LEVEL-Os: sycl-post-link{{.*}} "-Os"
 // CHK-POST-LINK-OPT-LEVEL-Oz: sycl-post-link{{.*}} "-Oz"
+
+// Verify header search dirs are added with -fsycl
+// RUN: %clang -### -fsycl %s 2>&1 | FileCheck %s -check-prefixes=CHECK-HEADER-DIR
+// RUN: %clang_cl -### -fsycl %s 2>&1 | FileCheck %s -check-prefixes=CHECK-HEADER-DIR
+// CHECK-HEADER-DIR: clang{{.*}} "-fsycl-is-device"{{.*}} "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl" "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include"
+// CHECK-HEADER-DIR: clang{{.*}} "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include{{[/\\]+}}sycl" "-internal-isystem" "{{.*}}bin{{[/\\]+}}..{{[/\\]+}}include"{{.*}} "-fsycl-is-host"