The BLAS library used by PETSc is not found by GSL in Fedora

[gtheler]

The GNU GSL needs a BLAS implementation to work. To enhance flexibility and allow different BLAS implementations to be used, even though it provides a libgslcblas it is not automatically linked when linking against libgsl.

Since PETSc is already linked agains a BLAS implementation and chances are that this implementation is more efficient than libgslcblas, configure does not link against libgslcblas if PETSc is found. This works well in Debian but does not work in Fedora, that uses libflexiblas that exports the symbol cblas_dgemm that configure searchs for but it is not found during linking.

Source: #4

[gtheler]

For now FeenoX will link against gsclbas even if PETSc is found (see 0da38bb). Still, I'd like to leave this open until we find a better solution.