The commit 08fdc970 (main/llvm: update to 3.6.1) moved from
autotools/configure to cmake build. The cmake build no longer builds
libLLVM-<version>.so which was used by mesa. Instead it builds more
granular libs. So we need to rebuild mesa.

see also https://llvm.org/bugs/show_bug.cgi?id=15493

the lazy linking does not work with musl anyway.

ref #4254

This is a temp workaround til the toolchain default to 586

The glx tls causes segfault with musl libc:
https://bugs.freedesktop.org/show_bug.cgi?id=35268

The glx tls is there for performance reasons that only affects glibc. On
musl libc it should not make any difference so we simply disable it.

probably not needed