test: use modified path in test

The Windows spawn_with_an_odd_path test builds a PATH variable that
starts with ";.;". However, the old path is then used to run the test.
This commit updates the test to use the new path.

PR: libuv#184
Reviewed-by: Bert Belder <bertbelder@gmail.com>

test/test-spawn.c

@@ -1015,7 +1015,7 @@ TEST_IMPL(spawn_with_an_odd_path) {
   char *path = getenv("PATH");
   ASSERT(path != NULL);
   snprintf(newpath, 2048, ";.;%s", path);
-  SetEnvironmentVariable("PATH", path);
+  SetEnvironmentVariable("PATH", newpath);
 
   init_process_options("", exit_cb);
   options.file = options.args[0] = "program-that-had-better-not-exist";