Add -parse-stdlib to macOS target test so it builds on Linux.

Author: allevato

test/DebugInfo/compiler-flags-macosx.swift

@@ -1,8 +1,8 @@
 // Check that the sdk and resource dirs end up in the debug info if we build for
 // a Darwin target and set the RC_DEBUG_OPTIONS environment variable. This
 // matches the behavior found in Clang.
-// RUN: %swiftc_driver %s -emit-ir -g -target x86_64-apple-macosx10.10 -o - | %FileCheck %s
-// RUN: RC_DEBUG_OPTIONS=1 %swiftc_driver %s -emit-ir -g -target x86_64-apple-macosx10.10 -o - | %FileCheck --check-prefix CHECK-VAR-SET %s
+// RUN: %swiftc_driver %s -emit-ir -g -target x86_64-apple-macosx10.10 -parse-stdlib -module-name scratch -o - | %FileCheck %s
+// RUN: RC_DEBUG_OPTIONS=1 %swiftc_driver %s -emit-ir -g -target x86_64-apple-macosx10.10 -parse-stdlib -module-name scratch -o - | %FileCheck --check-prefix CHECK-VAR-SET %s
 // CHECK:               !DICompileUnit({{.*}} producer: "{{(Apple )?Swift version [^"]+}}"
 // CHECK-NOT:                          flags: "
 // CHECK-VAR-SET:       !DICompileUnit({{.*}}producer: "{{(Apple )?Swift version [^"]+}}"