Keg#fix_install_names punts if bad install names reference dylibs that
aren't "nearby". Enable this machinery to fix more complex directory
hierarchies by searching everything under 'lib' for the bad name's
basename.
Additionally, teach it to correctly handle Mach-O bundle files.
FixesHomebrew/homebrew#12810.
Signed-off-by: Jack Nagel <jacknagel@gmail.com>