Windows GNU toolchain prevents static linking

[GrygrFlzr]

Currently, stdc++ must be linked dynamically for GNU toolchains to build from source:

if target.ends_with("-pc-windows-gnu") {
    println!("cargo:rustc-link-lib=dylib=stdc++");
}

This is solvable by rust-lang/rust#37403 via the use of this unstable feature:

• Add #![feature(static_nobundle)] to both lib.rs and build.rs of glsl-to-spirv-builder
• Modify the link to use static-nobundle:

if target.ends_with("-pc-windows-gnu") {
    println!("cargo:rustc-link-lib=static-nobundle=stdc++");
}

$ cargo +nightly-gnu test --release --target x86_64-pc-windows-gnu
   Compiling bevy-glsl-to-spirv-builder v0.1.0 (C:\Users\GrygrFlzr\Documents\projects\glsl-to-spirv\glsl-to-spirv-builder)
   Compiling bevy-glsl-to-spirv v0.2.2 (C:\Users\GrygrFlzr\Documents\projects\glsl-to-spirv)
    Finished release [optimized] target(s) in 1.77s
     Running target\x86_64-pc-windows-gnu\release\deps\bevy_glsl_to_spirv-aeb5d0f8868f37b0.exe

running 0 tests

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

     Running target\x86_64-pc-windows-gnu\release\deps\test-fe3b922dfa91430d.exe

running 1 test
test test1 ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.03s

   Doc-tests bevy-glsl-to-spirv

running 0 tests

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

Of course, this will not build without nightly, so this issue is blocked until the feature is stabilized.