linux/musl: Fix multiple definitions of MAP_HUGETLB

[taiki-e]

Currently, the build for powerpc-unknown-linux-musl is failing due to multiple definitions of MAP_HUGETLB.

$ cargo build -Zbuild-std=core --target powerpc-unknown-linux-musl
   Compiling libc v0.2.147 (...)
error[E0428]: the name `MAP_HUGETLB` is defined multiple times
   --> src/unix/linux_like/linux/musl/b32/powerpc.rs:383:1
    |
257 | pub const MAP_HUGETLB: ::c_int = 0x040000;
    | ------------------------------------------ previous definition of the value `MAP_HUGETLB` here
...
383 | pub const MAP_HUGETLB: ::c_int = 0x040000;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `MAP_HUGETLB` redefined here
    |
    = note: `MAP_HUGETLB` must be defined only once in the value namespace of this module

For more information about this error, try `rustc --explain E0428`.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

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[JohnTitor]

@bors r+

[bors]

📌 Commit cdc0fca has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit cdc0fca with merge 2bd687d...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing 2bd687d to main...