This is a bit of a blunt force solution to the issue... setting LDFLAGS like this will apply it to all GCC commands. However, it seems to be okay when I ran it on Travis.
A more surgical approach would be to apply these LDFLAGS only to ngslib, but this works.
The issue is that for some reason gcc is deciding not to link to libz even though the setup.py file for ngslib says -lz. Adding these LDFLAGS forces GCC to link to libz.
This is a bit of a blunt force solution to the issue... setting LDFLAGS like this will apply it to all GCC commands. However, it seems to be okay when I ran it on Travis.
A more surgical approach would be to apply these LDFLAGS only to ngslib, but this works.
The issue is that for some reason gcc is deciding not to link to libz even though the setup.py file for ngslib says
-lz
. Adding these LDFLAGS forces GCC to link to libz.