Append to RPATH (instead of overwrite)

[thomaslima]

Closes #137

Test cases in #134

Not-implemented caveat: #134 (comment)

[ferdonline]

Hi @thomaslima
Any update on this PR? In our project we also depend on internal libraries and require the previous RPATH to be respected.
Independently I arrived to a very similar solution.

prev_rpath = check_output(['patchelf', '--print-rpath', fn]).decode().rstrip('\n\t /')
check_call(['patchelf', '--remove-rpath', fn])
if prev_rpath and prev_rpath != rpath:
    rpath += ":" + prev_rpath

Feel free to use it.
In this PR, however, it seems the tests fail for some unrelated reason.
We would be happy to help this getting fixed. Thanks!

[thomaslima]

@ferdonline I'd really like some help. I have absolutely no time to look into this at the moment =(

[fbrennen]

Hi @thomaslima -- I had a quick go at updating your PR here: #245

[lkollar]

#245 implemented this.