This makes the output much less noisy and consistent with the other tests.

This makes the test fail on the first error and is consistent with all the
other intergration test scripts.

This makes the bash cmdline arguments consistent between running on Windows
and on other platforms using the `#!/bin/sh -e`.

For some reason this file that exists as src/isprefix.h was duplicated in the
tests directory.

Putting the quotes around it makes it try to execute a command called "bash
-e" instead of seeing the `-e` as another argument.