rework logic to avoid cluttering $PWD

Rather than trying to play games with detecting the status of the build
directory in $PWD, just create our own. This means we have a second
tempdir to deal with, and we introduce a more global method of handling
cleanup of them.
cleanup test log files with `make clean`
remove useless inheritance
repackage tarballs with fakeroot, if possible

1) wrap tinfoil around head
2) ???????????
3) profit!
fix tmpdir creation. subshells are hard.
pass extra args to makepkg
Revert "pass extra args to makepkg"

This reverts commit 367b212e8ecc414e88dcab271479a7488b8174e3.
mkaurball support '-p <file>' similar to makepkg

[dave: fix quoting, and declaration of buildfile]
changes to make it work on osx