Enable incremental for release mode via [profile.<...>] overrides.

Cargo.toml

@@ -16,17 +16,20 @@ members = [
     "tests/deps-helper",
 ]
 
-# Compile build-dependencies in release mode with
-# the same settings as regular dependencies.
-[profile.release.build-override]
-opt-level = 3
-codegen-units = 16
-
+# 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]` above
+# will treat the identical settings in `[profile.release.build-override]` below
 # as different sets of `rustc` flags and will not reuse artifacts between them.
-[profile.release]
-codegen-units = 16
+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
 
 [patch.crates-io]
 spirv-std = { path = "./crates/spirv-std" }