ci: add loongarch64

Author: inkydragon

.github/workflows/cross.yml

@@ -31,6 +31,7 @@ jobs:
           # - { arch: mips64el, triple: mips64el-linux-gnuabi64 }
           - { arch: riscv64,  triple: riscv64-linux-gnu }
           - { arch: s390x,    triple: s390x-linux-gnu }
+          - { arch: loongarch64, triple: loongarch64-linux-gnu }
     env:
       ARCH: ${{ matrix.config.arch }}
       TRIPLE: ${{ matrix.config.triple }}