autoconf: Adjust to new asm SOURCES variables

Commit 90b2beb661f630966788a6e909dc759c99e38973 changed the assembly
variables. Without this change, the glapi assembly wasn't being built
when it was supposed to, resulting in missing symbols in libGL.

Signed-off-by: Dan Nicholson <dbn.lists@gmail.com>
2 files changed