srt: fix install_name in macOS

see: https://github.com/Haivision/srt/pull/524
Fixes #63
3 jobs for issue-93 in 41 minutes and 37 seconds
Status Job ID Name Coverage
  Preparation
passed #73366
manifest

00:00:34

 
  Build
passed #73367
cerbero deps fedora x86_64

00:34:48

 
  Full Builds
passed #73368
build cerbero fedora x86_64

00:06:14