math/blis: update to the first snapshot working on FreeBSD to support runtime kernel selection. For amd64, this will now select, if available, an assembly optimized kernel for the CPU architecture blis is running on. The other architectures continue to only use what is now called the generic kernel but in theory arm and power7 assembly optimizations are available.
Due to this, remove the old explicit kernel selection. Also switch to use devel/llvm50 as a compiler to actually support all the architectures (and upstream compile flags) properly. This hopefully will also help with getting blis to work on other architectures out of the box.
Reviewed by: swills (mentor)
Approved by: swills (mentor)
Differential Revision: https://reviews.freebsd.org/D13264