Revert insiduous suppression of the -fopenmp flag in the LAPACK subtree
Revert insiduous suppression of the -fopenmp flag in the LAPACK subtree

This was added in #1046 citing a problem with mingw, but in effect it quietly reduces thread safety on all non-Windows platforms (while -fopenmp is already disabled for Windows builds through the toplevel Makefile.system). Removing the filter fixes #1425
xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,kortschak/OpenBLAS,xianyi/OpenBLAS,kortschak/OpenBLAS,xianyi/OpenBLAS,kortschak/OpenBLAS,kortschak/OpenBLAS,kortschak/OpenBLAS,xianyi/OpenBLAS,kortschak/OpenBLAS,kortschak/OpenBLAS,kortschak/OpenBLAS,xianyi/OpenBLAS,kortschak/OpenBLAS,xianyi/OpenBLAS