runtests should refer to test files in current directory

Recently added entry point renaming file referred to
test source file hlsl.entry.rename.frag via relative directory.

Change it to be consistent with other tests: assume test
sources are in the current directory.

Test/baseResults/hlsl.entry.rename.frag.out

@@ -1,4 +1,4 @@
-../Test/hlsl.entry.rename.frag
+hlsl.entry.rename.frag
 Shader version: 450
 gl_FragCoord origin is upper left
 0:? Sequence