Use clang+mold on linux (#12944)

Takes a clean build on my machine from 222s to 185s

Release Notes:

- N/A

.cargo/config.toml

@@ -4,3 +4,7 @@ rustflags = ["-C", "symbol-mangling-version=v0", "--cfg", "tokio_unstable"]
 
 [alias]
 xtask = "run --package xtask --"
+
+[target.x86_64-unknown-linux-gnu]
+linker = "/usr/bin/clang"
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]

script/linux

@@ -24,6 +24,8 @@ if [[ -n $apt ]]; then
     libvulkan1
     libgit2-dev
     make
+    clang
+    mold
   )
   $maysudo "$apt" install -y "${deps[@]}"
   exit 0
@@ -36,6 +38,8 @@ if [[ -n $dnf ]]; then
   deps=(
     gcc
     g++
+    clang
+    mold
     alsa-lib-devel
     fontconfig-devel
     wayland-devel