Add -lm to travis install script for OpenBLAS

[vladimir-ch]

No description provided.

[vladimir-ch]

Ok, so this passes. I think we don't have to worry about the coverage in #154. The percentage numbers are computed live: when I submitted this PR, the coverage numbers were the same as in #154 and there were changing as the build progressed. coveralls seems strange and buggy anyway, the summary claimed coverage increase while at the same time all the files had their coverage unchanged.

[jonlawlor]

I have no idea if the coverage numbers will be right on something that doesn't link correctly, I would ignore coveralls unless it is the only failed check.

[kortschak]

It would be nice to know what has changed to make this necessary. @xianyi do you have any ideas?

LGTM

[vladimir-ch]

I think I have solved it. For some reason the installation of gfortran in .travis/linux/OpenBLAS/install.sh failed with:

Failed to fetch http://us-central1.gce.archive.ubuntu.com/ubuntu/pool/main/g/gcc-4.6/gfortran-4.6_4.6.3-1ubuntu5_amd64.deb  503  Service Unavailable [IP: 173.255.118.228 80]

By the time I submitted this PR, the service probably became available and the build succeeded. So while this PR does not do any harm, it probably does not help either. Therefore I will close it.

On the other hand: the installation failure was hidden in the collapsed part of travis log. It would be better to have the install script fail in that case to clearly see the reason. Do you think it is doable, @jonlawlor ?

[xianyi]

@kortschak , I have no idea about this issue.

[jonlawlor]

I think if I set the exit status of the install script it will show up in the travis log. I'll see what I can do.