flintlib: update to 2.8.5.

[tornaria]

Also, enable openblas (used for matrix multiplication)

Testing the changes

• I tested the changes in this PR: YES

I ran sagemath long doctest suite with this. The update by itself is just a bugfix release, but I also took the chance to enable openblas for matrix multiplication so I wanted to make sure I didn't mess up (I had it disabled b/c of a misunderstanding on my part, it seems convenient to have it enabled.)

[tornaria]

Cross compilation fails with

mul_blas.c:24:10: fatal error: cblas.h: No such file or directory
   24 | #include "cblas.h"
      |          ^~~~~~~~~

This file is in /usr/include/openblas/cblas.h.

I added export EXTRA_INC_DIRS="/usr/include/openblas" to the template to fix this in normal build, but it seems to be ignored by cross builds... Any ideas?

Maybe I should just add -I/usr/include/openblas to CFLAGS?

[tornaria]

🤦 of course the answer is to use ${XBPS_CROSS_BASE}/usr/include/openblas instead, which will work on both cases.

I also simplified the template a little bit and avoid all the warnings from wrong -I/usr/include and -L/usr/lib.