Issue 37037: Enable rpath remapping in makefile

I'd like to be able to build libpython and have it already have the install path stripped out so I can use rpath instead. This libpython is going to be distributed with other applications.

Right now, I'm running `install_name_tool -id "@rpath/libpython3.7m.dylib" libpython3.7m.dylib` as a post-build step, (and will then have to figure out what breaks next ;) )

It's probably a simple makefile/autoconf update to add an option to run the necessary commands as part of build, but I can't figure it out myself. So I'm hoping someone can help or has already done it and wants to share.