Fails to compile on arch linux with openblas

[skwerlman]

on arch with openblas, compilation fails with the following error:

a5% mix compile
==> matrex
Compiling: native/src/matrix_dot.c
native/src/matrix_dot.c:5:10: fatal error: cblas.h: No such file or directory
    5 | #include <cblas.h>
      |          ^~~~~~~~~
compilation terminated.
make: *** [Makefile:200: _build/obj/matrix_dot.o] Error 1
could not compile dependency :matrex, "mix compile" failed. Errors may have been logged above. You can recompile this dependency with "mix deps.compile matrex --force", update it with "mix deps.update matrex" or clean it with "mix deps.clean matrex"

cblas.h exists at /usr/include/openblas/cblas.h

if i manually edit matrix_dot.c to have #include <openblas/cblas.h> instead, compilation succeeds