Kludging an install to workaround the gfortran/x87 compiler bug

ATLAS defaults to using gcc/gfortran 4.6, which unfortunately has a compiler bug when using the x87 unit. In this case, the Fortran77 BLAS and LAPACK testers must be compiled with low optimization, or they will (erroneously) show failures in every routine. In order to get around this problem, install as normal, but do not issue the make check or any other testing command. After the build is complete, edit your Make.inc, and scope the F77FLAGS macro. If it has the flag -mfpmath=387 anywhere in it, then you must append -O1 to it in order for gfortran 4.6 to properly compile the testers. If you make this change before the build, it will slow down all Fortran routines (eg., many lapack routines), which does not seem necessary to defeat the compiler bug.

R. Clint Whaley 2016-07-28