OS X: gcc -fopenmp requires DLYD_FALLBACK_LIBRARY_PATH to be set

[molpopgen]

This seems new, and was noticed when some CI builds using miniconda started failing.

System is El Capitan:

Darwin Kevins-MacBook-Pro-2.local 15.6.0 Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.60.10~1/RELEASE_X86_64 x86_64

I created a fresh user account and installed Anaconda/latest/OS X/64 bit/Python 3:

conda --version
conda 4.3.13

I then installed gcc and created the following C file:

#include <stdio.h>

int main(int argc, char **argv)
{
}

Compiling with -fopenmp causes a runtime issue that is fixed by setting DYLD_FALLBACK_LIBRARY_PATH. My understanding is that things are meant to work without declaring these:

Kevins-MacBook-Pro-2:~ condatest$ gcc -o test test.c
Kevins-MacBook-Pro-2:~ condatest$ ./test
Kevins-MacBook-Pro-2:~ condatest$ gcc -fopenmp -o test test.c 
Kevins-MacBook-Pro-2:~ condatest$ ./test
dyld: Library not loaded: @rpath/libgomp.1.dylib
  Referenced from: /Users/condatest/./test
  Reason: image not found
Trace/BPT trap: 5
Kevins-MacBook-Pro-2:~ condatest$ DYLD_FALLBACK_LIBRARY_PATH=$HOME/anaconda3/lib ./test

The issue seems specific to libgomp. Other C libraries work as expected. For example, after "conda install gsl", things work as expected:

Kevins-MacBook-Pro-2:~ condatest$ gcc  -o test test.c -lgsl -lgslcblas
Kevins-MacBook-Pro-2:~ condatest$ ./test