Properly handle rpath on macOS

Without this, the install_name of JAlienROOT is libJAlienROOT rather than
@rpath/libJAlienROOT, with the result things might break when SIP is
enabled.
1 job for fix-rpath in 35 seconds (queued for 1 second)
Status Name Job ID Coverage
  Start
failed build-start #12587453

00:00:35

 
Name Stage Failure
failed
build-start Start
Polling for status failed: 403: 403 Forbidden

Polling for status failed: 403: 403 Forbidden
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curl -s -X GET -H "PRIVATE-TOKEN: <private token>" https://gitlab.cern.ch/api/v4/projects/46440/pipelines/2386971
check your api token, or check if there are connection issues.

Cleaning up file based variables
ERROR: Job failed: exit code 2