clapack: fix build with musl

Fixes
http://autobuild.buildroot.net/results/a94f097193cd5444dee5cd9df9d544ce736a7e7e/
http://autobuild.buildroot.net/results/036014e492f7caf793b92a9822ab6a0b1a54f2e8/



Signed-off-by: Alex Suykov <alex.suykov@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>