add haiku support

[hoanga]

hello, the following updates adds support for building on haiku. below is an example run:

> uname -a
Haiku shredder 1 hrev57257 Sep  3 2023 06:27:36 x86_64 x86_64 Haiku

> cargo test
   Compiling libc v0.2.147
   Compiling log v0.4.20
   Compiling env_logger v0.7.1
   Compiling uzers v0.11.2 (/boot/home/src/git/rust-libs/uzers-rs)
    Finished test [unoptimized + debuginfo] target(s) in 12.25s
     Running unittests src/lib.rs (target/debug/deps/uzers-07f1336e770b9cb7)

running 18 tests
test base::test::uid ... ok
test base::test::group_by_name ... ok
test base::test::user_by_name ... ok
test base::test::uid_for_username ... ok
test base::test::user_info ... ok
test base::test::user_get_groups ... ok
test base::test::username_for_uid_for_username ... ok
test base::test::username ... ok
test mock::test::gid ... ok
test mock::test::current_username ... ok
test mock::test::group_name ... ok
test mock::test::no_current_username ... ok
test mock::test::no_gid ... ok
test mock::test::no_group_name ... ok
test mock::test::no_uid ... ok
test mock::test::no_username ... ok
test mock::test::uid ... ok
test mock::test::username ... ok

test result: ok. 18 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests uzers

running 40 tests
test src/base.rs - base::User::groups (line 138) - compile ... ok
test src/base.rs - base::Group::new (line 185) ... ok
test src/base.rs - base::Group::name (line 219) ... ok
test src/base.rs - base::Group::gid (line 205) ... ok
test src/base.rs - base::User::name (line 104) ... ok
test src/base.rs - base::User::new (line 69) ... ok
test src/base.rs - base::User::primary_group_id (line 119) ... ok
test src/base.rs - base::User::uid (line 90) ... ok
test src/base.rs - base::all_groups (line 951) ... ok
test src/base.rs - base::all_users (line 863) ... ok
test src/base.rs - base::get_current_gid (line 654) ... ok
test src/base.rs - base::get_current_groupname (line 675) ... ok
test src/base.rs - base::get_current_uid (line 563) ... ok
test src/base.rs - base::get_current_username (line 587) ... ok
test src/base.rs - base::get_effective_gid (line 698) ... ok
test src/base.rs - base::get_effective_uid (line 610) ... ok
test src/base.rs - base::get_effective_groupname (line 719) ... ok
test src/base.rs - base::get_effective_username (line 631) ... ok
test src/base.rs - base::get_group_by_gid (line 444) ... ok
test src/base.rs - base::get_user_groups (line 784) - compile ... ok
test src/base.rs - base::get_user_by_name (line 376) ... ok
test src/base.rs - base::get_group_by_name (line 496) ... ok
test src/base.rs - base::group_access_list (line 747) - compile ... ok
test src/base.rs - base::get_user_by_uid (line 324) ... ok
test src/cache.rs - cache (line 11) - compile ... ok
test src/cache.rs - cache (line 47) - compile ... ok
test src/lib.rs - (line 101) - compile ... ok
test src/cache.rs - cache::UsersCache::new (line 151) ... ok
test src/cache.rs - cache::UsersCache::with_all_users (line 170) ... ok
test src/lib.rs - (line 42) ... ok
test src/lib.rs - (line 76) ... ok
test src/switch.rs - switch::set_both_gid (line 187) - compile ... ok
test src/switch.rs - switch::set_both_uid (line 156) - compile ... ok
test src/switch.rs - switch::set_current_gid (line 63) - compile ... ok
test src/switch.rs - switch::set_current_uid (line 32) - compile ... ok
test src/mock.rs - mock (line 19) ... ok
test src/switch.rs - switch::set_effective_gid (line 125) - compile ... ok
test src/mock.rs - mock (line 41) ... ok
test src/switch.rs - switch::set_effective_uid (line 94) - compile ... ok
test src/switch.rs - switch::switch_user_group (line 243) - compile ... ok

test result: ok. 40 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 4.78s

[gierens]

LGTM ... thanks for the contribution :)