Fix warnings in rs{begin,end}.rs files

[mati865]

As can be seen locally and in CI logs (dist-i686-mingw) that code used to trigger static_mut_refs warning.

[rustbot]

r? @Mark-Simulacrum

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[mati865]

Warnings from local build:

Creating a sysroot for stage1 compiler (use `rustup toolchain link 'name' build/host/stage1`)
warning: creating a mutable reference to mutable static
  --> G:\Projects\rust\library\rtstartup\rsbegin.rs:93:65
   |
93 |         __register_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &mut OBJ as *mut _ as *mut u8);
   |                                                                 ^^^^^^^^ mutable reference to mutable static
   |
   = note: for more information, see <https://doc.rust-lang.org/edition-guide/rust-2024/static-mut-references.html>
   = note: mutable references to mutable statics are dangerous; it's undefined behavior if any other pointer to the static is used or if any other reference is created for the static while the mutable reference lives
   = note: `#[warn(static_mut_refs)]` (part of `#[warn(rust_2024_compatibility)]`) on by default
help: use `&raw mut` instead to create a raw pointer
   |
93 |         __register_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &raw mut OBJ as *mut _ as *mut u8);
   |                                                                  +++

warning: creating a mutable reference to mutable static
  --> G:\Projects\rust\library\rtstartup\rsbegin.rs:98:67
   |
98 |         __deregister_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &mut OBJ as *mut _ as *mut u8);
   |                                                                   ^^^^^^^^ mutable reference to mutable static
   |
   = note: for more information, see <https://doc.rust-lang.org/edition-guide/rust-2024/static-mut-references.html>
   = note: mutable references to mutable statics are dangerous; it's undefined behavior if any other pointer to the static is used or if any other reference is created for the static while the mutable reference lives
help: use `&raw mut` instead to create a raw pointer
   |
98 |         __deregister_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &raw mut OBJ as *mut _ as *mut u8);
   |                                                                    +++

warning: 2 warnings emitted

[bjorn3]

Suggested change

	__register_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &raw mut OBJ as *mut _ as *mut u8);
	__register_frame_info(&__EH_FRAME_BEGIN__ as *const u8, &raw mut OBJ as *mut u8);

The first cast was just to get a raw pointer. Same below.

[mati865]

Oh, neat. It didn't occur to me this is the same as coercing.
I fell for "compiler warning says, monkey does".

[joboet]

@bors r+ rollup
r? joboet

[rust-bors]

📌 Commit 6c6f586 has been approved by joboet

It is now in the queue for this repository.