Problems with numpy and linking with blas libraries

[Joe Berner]

It seems like there's a history of issues here and different workarounds.
Some keywords would be "GCC_4.6.0", "cblas", possibly "libgfortran".

I was running into the issue with the most current port revision and after
a bunch of make / make clean cycles I've gotten it to compile and work just
by making changes to /usr/ports/math/py-numpy/files/site.cfg

1) Changing the variable "library_dirs" to be equal to /usr/lib/local/gcc49
, removing the other colon-separated alternatives. Not removing the other
alternatives resulted in the build failing.

2) Adding /usr/local/lib/gcc49/include to the "include_dirs" variable. I
did not have to remove the other variables.

It seems like the build system is preferentially trying to link against one
of the openblas.so files in /usr/local/lib as opposed to (say)
/usr/local/lib/gcc49 . However the one in /usr/local/lib has incompatible
versions on my system, and so the compile fails.

Trying this again*, the build also works compiled against the corresponding
gcc6 folders instead of gcc49. I am using the pkg-provided gcc6.

Hopefully this information helps wiser people solve the problem for others.

Joe

*: Trying again in this case means make clean, changing things then make
deinstall,  make reinstall, and runnin numpy.test(label='fast', verbose=10)
in python3.6.