add build script optimizations from rust-gpu for spirv-builder variant

Author: Firestar99

ash-graphics/Cargo.toml.liquid

@@ -33,3 +33,32 @@ raw-window-handle = "0.6.2"
 winit = "0.30.0"
 cfg-if = "1.0.0"
 anyhow = "1.0.98"
+
+{% if integration_type == "spirv-builder" -%}
+# Optimize build scripts, copied from rust-gpu's repo
+# Enable incremental by default in release mode.
+[profile.release]
+incremental = true
+# HACK(eddyb) this is the default but without explicitly specifying it, Cargo
+# will treat the identical settings in `[profile.release.build-override]` below
+# as different sets of `rustc` flags and will not reuse artifacts between them.
+codegen-units = 256
+
+# Compile build-dependencies in release mode with the same settings
+# as regular dependencies (including the incremental enabled above).
+[profile.release.build-override]
+opt-level = 3
+incremental = true
+codegen-units = 256
+
+# HACK(eddyb) reduce the number of linker exports and/or imports, by avoiding
+# inter-CGU linkage, to stay under the 64Ki MSVC limit for `rustc_codegen_spirv`
+# when building it in "debug mode" (only relevant to CI for now, realistically),
+# i.e. working around this issue: https://github.com/rust-lang/rust/issues/53014.
+[profile.dev]
+# HACK(eddyb) fewer inter-crate exports/imports (not just inter-CGU), but sadly
+# not configurable w/o breaking `Cargo.toml` parsing from non-nightly Cargo.
+#
+# rustflags = ["-Zshare-generics=off"]
+codegen-units = 1
+{% endif -%}