mips16.S was missing since
commit 29b7454553
Date: Thu Jun 1 10:14:24 2023 +0800
MIPS: Add speculation_barrier support
Without mips16.S included, some symbols will miss for mips16, and
so some software will fail to build.
libgcc/ChangeLog:
* config/mips/lib1funcs.S: Includes mips16.S.