Add linux/loongarch64 support in 'compiler/installer.ini'

[qiangxuhui]

The files(like build/build.sh)generated by the command koch csource do not contain complete linux/loongarch64 support. This patch will fix it.

[qiangxuhui]

Before patched(compare with riscv64):

## loongarch64
# grep -rn "loongarch" build/build.sh
234:  *loongarch64* )
235:    mycpu="loongarch64" ;;


## riscv64
# grep -rn "riscv64" build/build.sh
230:  *riscv64|riscv* )
231:    mycpu="riscv64" ;;
1355:  riscv64)
10064:  riscv64)
12593:  riscv64)
14638:  riscv64)
20515:  riscv64)
22568:  riscv64)
24621:  riscv64)
25718:  riscv64)
26337:  riscv64)
27430:  riscv64)
28999:  riscv64)
29616:  riscv64)

After patched:

# grep -rn "loongarch" build/build.sh
234:  *loongarch64* )
235:    mycpu="loongarch64" ;;
1362:  loongarch64)
10554:  loongarch64)
13090:  loongarch64)
15142:  loongarch64)
21504:  loongarch64)
23086:  loongarch64)
25146:  loongarch64)
26250:  loongarch64)
26876:  loongarch64)
27976:  loongarch64)
29552:  loongarch64)
30176:  loongarch64)

[github-actions]

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from 77c0409

Hint: mm: orc; opt: speed; options: -d:release
178623 lines; 8.310s; 753.102MiB peakmem