i965: automake: include builddir prior to srcdir
i965: automake: include builddir prior to srcdir

The latter can contain stale generated file, which, as-is, we'll end up
using.

Fixes: bfd17c76c12 "i965: Port INTEL_PRECISE_TRIG=1 to NIR."
Cc: "12.0 13.0" <4a7dc73e2393621c9290144a497188a9d4f7d87e@lists.freedesktop.org>
Cc: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Signed-off-by: Emil Velikov <4c996f2f093ddd0585a556460b4cc3ba555546ef@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler