My global config.toml setup for ultra fast Rust compile times

config.toml

[unstable]
codegen-backend = true

[profile.dev]
# Compile using cranelift for massively faster compilation
codegen-backend = "cranelift"
# If you want to attach a debugger, set `debug = true` instead
debug = "line-tables-only"
# Assuming we don't do `catch_unwind`, we can safely abort on panics for some extra perf
panic = "abort"

# Consider compiling deps with cranelift if you want cold-compilation to be faster
# Or, if you want your hot compilation to have max performance, copy the contents of `[profile.dev.build-override]` here
# The setting below is a happy medium between performance and cold compile time.
[profile.dev.package."*"]
codegen-backend = "llvm"

# cranelift is always `panic = abort`, so you need to compile with llvm to get `#[should_panic]` working
# See <https://github.com/rust-lang/rust/issues/32512>
[profile.test.package."*"]
codegen-backend = "llvm"

# Enable optimizations for build scripts and proc-macros
# This trades slower cold compilation for faster incremental compilation
[profile.dev.build-override]
codegen-backend = "llvm"
codegen-units = 1
opt-level = 3

# Disable cranelift for release profile,
# and trade some compile time for increased performance
[profile.release]
codegen-backend = "llvm"
codegen-units = 1
# lto = "fat" has very diminishing returns on performance, but extremely high compile times
# "thin" is good enough.
lto = "thin"
# Assuming we don't do `catch_unwind`, we can safely abort on panics for some extra perf
panic = "abort"

# cranelift cannot build wasm32-unknown-unknown out of the box
[profile.web]
codegen-backend = "llvm"

[build]
# Using a global target dir allows all projects to share incremental compilation results,
# vastly speeding up cold-compilation of new projects.
target-dir = "/home/hhh/.cargo/global-target"

[target.x86_64-unknown-linux-gnu]
linker = "clang"
rustflags = [
    "-Clink-arg=--ld-path=wild",
    # Compile faster
    "-Zshare-generics=y",
    # 8 is the limit where parallelism overhead begins to dominate
    "-Zthreads=8",
    # optimize for the current CPU
    # remove this if you want to share the binary with others
    "-Ctarget-cpu=native",
]
rustdocflags = [
    # Compile faster
    "-Zshare-generics=y",
    # 8 is the limit where parallelism overhead begins to dominate
    "-Zthreads=8",
]

[target.wasm32-unknown-unknown]
rustflags = [
    # Compile faster
    "-Zshare-generics=y",
    # 8 is the limit where parallelism overhead begins to dominate
    "-Zthreads=8",
    # optimize for the current CPU
    # remove this if you want to share the binary with others
    "-Ctarget-cpu=native",
]
rustdocflags = [
    # Compile faster
    "-Zshare-generics=y",
    # 8 is the limit where parallelism overhead begins to dominate
    "-Zthreads=8",
]

Put the above in ~/.cargo/config.toml.
Requires:

• Linux
• nightly: rustup default nightly
• cranelift: rustup component add rustc-codegen-cranelift-preview --toolchain nightly
• wild linker: cargo install --locked wild-linker
• Bevy CLI: cargo install --git https://github.com/TheBevyFlock/bevy_cli --locked bevy_cli

and assumes you run your apps with bevy run and bevy run web -U multi-threading.
Also make sure to enable the dynamic_linking for Bevy!