verify if cblas.pc and lapack.pc should be replaced by links to openblas.pc

[dimpase]

currently openblas's spkg-configure.pc unconditionally makes cblas.pc and lapack.pc copies of openblas.pc, which in some cases if incorrect, e.g. Arch Linux has libcblas linked to libopenblas
and containing stuff missing in libopenblas, resulting in errors.

this has been reported on sage-devel
https://groups.google.com/d/msg/sage-devel/pIOnFyFJMtM/_FbzM2OxCQAJ

So we should make these installations conditional.

Depends on #29051

CC: @isuruf @mkoeppe @antonio-rojas

Component: build: configure

Author: Dima Pasechnik

Branch/Commit: 3a4524e

Reviewer: Isuru Fernando, Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/29071

[dimpase]

comment:1

It depends on the fortran name mangling. For gfortran, one symbol would be dgeqrf_.

we can do an AC_LINK_IFELSE() test with a subroutine dgeqef call,
and try to link it against libopenblas. this would be independent of Fortran compiler.

http://www.netlib.org/lapack/explore-html/df/dc5/group__variants_g_ecomputational_ga3766ea903391b5cf9008132f7440ec7b.html

[dimpase]

comment:2

And for cblas we can do AC_CHECK_LIB() on cblas_dgemm, as Antonio proposed.

[isuruf]

comment:3

You can also use AC_FC_FUNC to get the mangled name.

[dimpase]

comment:4

Replying to @isuruf:

You can also use AC_FC_FUNC to get the mangled name.

OK, that's better, thanks.

[dimpase]

Author: Dima Pasechnik

[dimpase]

Branch: u/dimpase/packages/openblaspcfix

[dimpase]

comment:5

needs testing on Arch in particular.

---

New commits:

ccc5d82

install cblas.pc and lapack.pc links conditionally

[dimpase]

Commit: ccc5d82

[videlec]

comment:6

trying now on arch

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

f6714fb

use AC_SEARCH_LIBS