Auto merge of #161243 - GuillaumeGomez:binutils-install, r=Kobzol

Do not install new binutils on the system, only use it in gcc



As discussed in #161218.

cc @RalfJung @antoyo 
r? @Kobzol

Author: bors

src/ci/docker/host-x86_64/dist-x86_64-linux/dist.sh

@@ -16,7 +16,23 @@ python3 ../x.py build --set rust.debug=true opt-dist
 # Use GCC for building GCC components, as it seems to behave badly when built with Clang
 # Only build GCC on full builds, not try builds
 if [ "${DIST_TRY_BUILD:-0}" == "0" ]; then
-    CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ python3 ../x.py dist \
-      gcc-dev \
-      gcc
+    # We add the binutils binary path to ensure that it uses the 2.47 version of binutils,
+    # which is needed for the `retain` attribute feature.
+    export PATH="/tmp/binutils-install/bin:$PATH"
+
+    CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ \
+        python3 ../x.py dist \
+        gcc-dev \
+        gcc
+
+    gcc_path="./build/$HOSTS/gcc/$HOSTS/install/bin/gcc"
+    if echo 'int x __attribute__((used, retain));' | \
+            "$gcc_path" -S -x c -o - - | grep -i '"a.*R"'; then
+        echo "retain attribute is supported"
+    else
+        echo "retain attribute is not supported"
+        # We display the generated asm just in case...
+        echo 'int x __attribute__((used, retain));' | "$gcc_path" -S -x c -o - -
+        exit 1
+    fi
 fi

src/ci/docker/scripts/build-gcc.sh

@@ -4,6 +4,30 @@ set -eux
 
 source shared.sh
 
+# We have to build our own binutils for the GCC build, because the default CentOS 7 binutils are
+# too old, and they do not support `SHF_GNU_RETAIN`.
+BINUTILS="2.47"
+BINUTILS_ROOT_PATH="$(pwd)/binutils-install"
+BINUTILS_PATH="$BINUTILS_ROOT_PATH/bin"
+curl https://ci-mirrors.rust-lang.org/rustc/gcc/binutils-$BINUTILS.tar.xz | xzcat | tar xf -
+mkdir binutils-build
+mkdir "$BINUTILS_ROOT_PATH"
+cd binutils-build
+
+hide_output ../binutils-$BINUTILS/configure --prefix="$BINUTILS_ROOT_PATH" --disable-werror
+hide_output make -j$(nproc)
+hide_output make install
+
+cd ..
+rm -rf binutils-build binutils-$BINUTILS
+
+if echo '.section .test,"awR",@progbits' | "$BINUTILS_PATH"/as - -o /dev/null 2>/dev/null; then
+    echo "binutils assembler supports SHF_GNU_RETAIN"
+else
+    echo "binutils assembler DOES NOT support SHF_GNU_RETAIN"
+    exit 1
+fi
+
 # Note: in the future when bumping to version 10.1.0, also take care of the sed block below.
 # This version is specified in the Dockerfile
 GCC=$GCC_VERSION