[DO NOT MERGE] bump(main/fish): 4.0b1

[TomJo2000]

This PR is intended for build testing.

DO NOT MERGE.

Fish 4.0 transitions the project to Rust.
Meaning we gotta write new patches.

CC: @AminurAlam

[Biswa96]

This probably needs some work for Android. For example, the first error was fixed in libc 0.2.165 version https://github.com/rust-lang/libc/releases/tag/0.2.165

[TomJo2000]

We're probably not going to wanna package the beta release anyway, this is just intended for testing.

[thunder-coding]

Assigning myself as I use the fish shell, so will try to test this out

[TomJo2000]

Push access for maintainers is enabled on this PR.
So feel free to push to this branch as necessary, or open up a new branch/PR.

[thunder-coding]

Rust's libc has no support for posix_spawn primitives. I'll create an issue upstream and try to create a PR as well with the fix.

The integer conversion errors also seem to be Rust libc bugs:

error[E0308]: mismatched types

   --> src/wutil/dir_iter.rs:115:50
    |
115 |             self.typ.set(stat_mode_to_entry_type(s.st_mode));
    |                          ----------------------- ^^^^^^^^^ expected `u16`, found `u32`
    |                          |
    |                          arguments to this function are incorrect

ino_t is defined as c_ulong whereas d_eno is of type u64. The correct behaviour is that ino_t should also be defined as ino_t like how it is done for Linux.
https://github.com/rust-lang/libc/blob/1867bf30eb9d22d3f8e86c2a8c25cf92fe5580da/src/unix/linux_like/android/mod.rs#L24
https://github.com/rust-lang/libc/blob/1867bf30eb9d22d3f8e86c2a8c25cf92fe5580da/src/unix/linux_like/android/mod.rs#L531

error[E0308]: mismatched types
   --> src/wutil/dir_iter.rs:115:50
    |
115 |             self.typ.set(stat_mode_to_entry_type(s.st_mode));
    |                          ----------------------- ^^^^^^^^^ expected `u16`, found `u32`
    |                          |
    |                          arguments to this function are incorrect

mod_t definition
https://github.com/rust-lang/libc/blob/1867bf30eb9d22d3f8e86c2a8c25cf92fe5580da/src/unix/linux_like/android/b32/mod.rs#L8
https://github.com/rust-lang/libc/blob/1867bf30eb9d22d3f8e86c2a8c25cf92fe5580da/src/unix/linux_like/android/b64/mod.rs#L8

st_mode definition:
https://github.com/search?q=repo%3Arust-lang%2Flibc+path%3A%2F%5Esrc%5C%2Funix%5C%2Flinux_like%5C%2F%2F+path%3A%2F%5Esrc%5C%2Funix%5C%2Flinux_like%5C%2Fandroid%5C%2F%2F+st_mode&type=code

mod_t should instead be c_uint and st_mode should have it's type as mod_t