srt recipe does not have the correct install_name on macOS
Submitted by Nirbheek Chauhan
The install_name is not set as the absolute path to the library, due to which the
srt plugin fails to load because it can't find libsrt.1.dylib.
This is likely because both these use cmake and don't use the correct incantation to set the install name as the absolute path. Openjpeg also uses cmake and does this correctly, so we should just copy what it does.