Remove slash from test. Win and Linux use a different charater.

Author: s-perron

clang/test/Driver/dxc_I.test

@@ -1,4 +1,4 @@
 // RUN: %clang_dxc -Tlib_6_3  -### %s 2>&1 | FileCheck %s
 
 // Make sure a non `.hlsl` file is considered an HLSL source file in dxc mode.
-// CHECK: "-x" "hlsl" "{{.*}}/dxc_I.test"
+// CHECK: "-x" "hlsl" "{{.*}}dxc_I.test"