clang/test/Driver/fsanitize.c: Fix -fsanitize=vptr using default target

The default implementation of getSupportedSanitizers isn't able to turn
on the vptr sanitizer, and thus, any platform that runs this test will
fail with the error:

    clang: error: unsupported option '-fsanitize=vptr' for target '<target>'

Patch by James Nagurne!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@365981 91177308-0d34-0410-b5e6-96231b3b80d8

test/Driver/fsanitize.c

@@ -97,7 +97,7 @@
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=vptr -fsanitize-undefined-trap-on-error %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-VPTR-TRAP-UNDEF
 // CHECK-VPTR-TRAP-UNDEF: error: invalid argument '-fsanitize=vptr' not allowed with '-fsanitize-trap=undefined'
 
-// RUN: %clang -fsanitize=vptr -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-VPTR-NO-RTTI
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=vptr -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-VPTR-NO-RTTI
 // CHECK-VPTR-NO-RTTI: '-fsanitize=vptr' not allowed with '-fno-rtti'
 
 // RUN: %clang -fsanitize=undefined -fno-rtti %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UNDEFINED-NO-RTTI