nir: fix nir_opt_algebraic.c compilation time on release build GCC 9.2
Gitlab issue: #825 (closed)
Due to commit f097247d, GCC 9.2 takes a lot of time compiling the autogenerated
nir_opt_algebraic.c file in a release build. It seems to be a compiler bug as it cannot be reproduced with GCC 8.3 nor 7.4. This patch changes the logic to have normal build values again.
@idr, can you test this patch?