[Bug target/106097] undefined behaviors regarding integer shifts in loongarch_build_integer

[chenglulu at loongson dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106097

--- Comment #11 from chenglulu <chenglulu at loongson dot cn> ---

> Otherwise LGTM.  As the port maintainer you can push it directly into
> master.  Normally we should bootstrap and regtest before applying a patch,
> but currently the bootstrap is blocked by PR106096 :(.
Ok, I will submit patches in order.