Bug 1680080 - Optimize proc macros / build dependencies. r=glandium,firefox-build-system-reviewers,mhentges

On a very parallel debug build, I see a long time just waiting for
bindgen / style compilation / geckoservo.

Turns out that a bunch of this is just proc macros / build scripts.

Optimizing it saves between 10 and 17 seconds of my debug build. We
might want to consider running bindgen much like cbindgen rather than
rebuilding it all the time, which should help a lot more, but my guess
is that this should still help with the pretty hot custom derives that
the style crate runs.

This needs rust 1.41, so the requirement for tools/crashreporter needs
to be bumped as a consequence. To make things simpler, it was bumped
to 1.47 while we're at it.

Differential Revision: https://phabricator.services.mozilla.com/D98366

Cargo.toml

@@ -63,6 +63,14 @@ rpath = false
 debug-assertions = false
 panic = "abort"
 
+# Optimize build dependencies, because bindgen and proc macros / style
+# compilation take more to run than to build otherwise.
+[profile.dev.build-override]
+opt-level = 1
+
+[profile.release.build-override]
+opt-level = 1
+
 [patch.crates-io]
 chardetng = { git = "https://github.com/hsivonen/chardetng", rev="7d5e0608d3e012bdfea3bd199111e3546607dd31" }
 libudev-sys = { path = "dom/webauthn/libudev-sys" }

build/moz.configure/rust.configure

@@ -165,7 +165,7 @@ def rust_compiler(rustc_info, cargo_info, build_project):
             )
         )
     if build_project == "tools/crashreporter":
-        rustc_min_version = Version("1.38.0")
+        rustc_min_version = Version("1.47.0")
     else:
         rustc_min_version = Version(MINIMUM_RUST_VERSION)
     cargo_min_version = rustc_min_version

config/makefiles/rust.mk

@@ -72,14 +72,11 @@ ifndef MOZ_LTO_RUST_CROSS
 ifeq (,$(findstring gkrust_gtest,$(RUST_LIBRARY_FILE)))
 cargo_rustc_flags += -Clto
 endif
-# Versions of rust >= 1.45 need -Cembed-bitcode=yes for all crates when
-# using -Clto.
-ifeq (,$(filter 1.38.% 1.39.% 1.40.% 1.41.% 1.42.% 1.43.% 1.44.%,$(RUSTC_VERSION)))
+# We need -Cembed-bitcode=yes for all crates when using -Clto.
 RUSTFLAGS += -Cembed-bitcode=yes
 endif
 endif
 endif
-endif
 
 ifdef CARGO_INCREMENTAL
 export CARGO_INCREMENTAL