Initial version.
Fix permissions on some files.
Don't even mention of cleaning ${TGT} in do-setup-target-dir.sh

(do-build-all.sh could be called multiple times in case of errors, and
the target directory shouldn't be nuked obviously).
Minor fix for do-build-bzip2.sh
Fix python version in PKG_URL in do-build-python26.sh
Add alembic_build/ to .gitignore