Add support for LoongArch64

[heiher]

Add support for LoongArch64 (A tier-2 with host tools target).

[heiher]

Test resutls

PASSED

cargo test --features instrumentation

running 36 tests
test compress::tests::test_compression_from_str ... ok
test db::tests::test_db_open_should_fail ... ok
test compress::tests::test_compression_interfaces ... ok
test index::test::test_entries ... ok
test index::test::test_find_entries ... ok
test index::test::test_find_entry_same_value ... ok
test index::test::test_find_entry_zero_pk ... ok
test index::test::test_find_any_entry ... ok
test table::test::oversized_into_fixed_panics - should panic ... ok
test table::test::bad_size_header ... ok
test table::test::insert_simple ... ok
test db::tests::test_partial_log_recovery ... ok
test table::test::ref_underflow ... ok
test table::test::remove_simple ... ok
test table::test::replace_multipart_shorter ... ok
test table::test::ref_counting ... ok
test db::tests::test_recover_from_log_on_error ... ok
test table::test::replace_simple ... ok
test table::test::replace_multipart_longer ... ok
test db::tests::test_db_open_fail_then_recursively_create ... ok
test db::tests::test_db_open_or_create ... ok
test table::test::multipart_collision ... ok
test migration::test::clear_column ... ok
test db::tests::test_add_column ... ok
test db::tests::test_indexed_keyvalues ... ok
test db::tests::test_remove_column ... ok
test db::tests::test_indexed_overlay_against_backend ... ok
test db::tests::test_indexed_btree_1 ... ok
test table::test::iteration ... ok
test db::tests::test_indexed_btree_2 ... ok
test migration::test::migrate_simple ... ok
test db::tests::test_continue_reindex ... ok
test db::tests::test_indexed_btree_3 ... ok
test db::tests::test_simple ... ok
test db::tests::test_btree_iter ... ok
test db::tests::test_random ... ok

test result: ok. 36 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 10.03s

     Running tests/loom.rs (target/debug/deps/loom-3e812a113b89ec98)

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests parity-db

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

[arkpar]

Thank you for the PR.
We can't support it officially since there's not CI for this platform. There's a chance that something may break in future releases and the maintainers have no way to debug and test fixes.
It should be possible to setup a qemu-based CI action for running tests at least, but I could not find any readily available solution for this.

[heiher]

Thanks for your review. I'll add CI when it's ready.