Bug#1050764: scm: Please add support for new arch Loongarch

[zhaixiaoj...@loongson.cn]

Dear Maintainer,

I also submitted the relevant patch to 
salsa.debian.org(https://salsa.debian.org/scheme-team/scm/-/merge_requests/3 
<https://salsa.debian.org/scheme-team/scm/-/merge_requests/3>).

Could you consider merging this patch?