Correct yet more usage of paths, and strip \n off build config lines.

From now on, build_component.py should not be `execfile`'d from
a wrapper script but rather `import`'ed and its `main()` run.
This will make all of our usage of `__file__` and `os.path` work
as expected.

(For the curious: Using `execfile` makes the target's `__file__`
contain the *caller's* `__file__`, and thus path. Calling the
callee by other means results in other, viz. the *correct* contents,
which might turn out inappropriate for your program logic).
Typo