startup code for aarch64-windows fails to build

[Techatrix]

Zig Version

0.15.0-dev.875+75d6d4c3f

Steps to Reproduce and Observed Behavior

// main.zig
pub fn main() void {}

Try to compile it to aarch64-windows:

zig build-exe -target aarch64-windows main.zig --color off

This will output the following error:

error: <inline asm>:1:2: unrecognized instruction mnemonic
        fninit
        ^

A bisect indicates that this regression has been caused by #24193. Probably by the changes to lib/std/start.zig which started to call fninit.

Expected Behavior

Produce a valid aarch64-windows executable.

[alexrp]

Fix for this is included in #24146.