rust: build with PGO in CLANG64

mingw-w64-rust/PKGBUILD

@@ -17,7 +17,7 @@ pkgname=("${MINGW_PACKAGE_PREFIX}-${_realname}"
          $([[ ${CARCH} == i686 ]] || echo "${MINGW_PACKAGE_PREFIX}-rust-wasm")
          "${MINGW_PACKAGE_PREFIX}-rust-src")
 pkgver=1.83.0
-pkgrel=3
+pkgrel=4
 pkgdesc="Systems programming language focused on safety, speed and concurrency (mingw-w64)"
 arch=('any')
 mingw_arch=('mingw32' 'mingw64' 'ucrt64' 'clang64' 'clangarm64')
@@ -176,6 +176,16 @@ build() {
   _rust_build+=("--stage" "2")
   #_rust_build+=("--verbose")
 
+  # compile rustc at first to generate PGO profile
+  if [[ ${MSYSTEM} == CLANG64 ]]; then
+    python ../${_realname}c-${pkgver}-src/x.py build "${_rust_build[@]}" \
+      --target="$OSTYPE" \
+      --rust-profile-generate="$PWD"/rust-pgo
+
+    llvm-profdata merge "$PWD"/rust-pgo/*.profraw --output="$PWD"/rust.profdata
+    _rust_build+=("--rust-profile-use=$PWD/rust.profdata")
+  fi
+
   # create the install at a temporary directory
   DESTDIR="$PWD"/dest-rust python ../${_realname}c-${pkgver}-src/x.py install "${_rust_build[@]}"