build-bisect.py: Minor tweaks and Mac fix
build-bisect.py: Minor tweaks and Mac fix

* Allow user-specified profile directories.
* Fix Mac BUILD_EXE_NAME to be the actual binary, rather than the bundle.

Review URL: http://codereview.chromium.org/209045

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@26662 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser