[GITHUB] Add gcc-8.4.0.tar.xz fallback workaround for RosBE build script

ftpmirror.gnu.org is returning Gateway Timeout / Bad Gateway errors lately.

Author: binarymaster

.github/workflows/build.yml

@@ -26,6 +26,8 @@ jobs:
         echo march-sha=$(gcc -march=native -Q --help=target | sha1sum | awk '{print $1}') >> $GITHUB_OUTPUT
         echo git-sha=$(git ls-remote https://github.com/zefklop/RosBE.git | grep unix_amd64 | awk '{print $1}') >> $GITHUB_OUTPUT
         wget https://gist.githubusercontent.com/zefklop/b2d6a0b470c70183e93d5285a03f5899/raw/build_rosbe_ci.sh
+        # Fallback for GNU file server problems.
+        sed -i '/gcc-8.4.0\/gcc-8.4.0.tar.xz/c\wget https://ftpmirror.gnu.org/gcc/gcc-8.4.0/gcc-8.4.0.tar.xz || wget -L https://web.archive.org/web/2025if_/https://ftpmirror.gnu.org/gcc/gcc-8.4.0/gcc-8.4.0.tar.xz' ./build_rosbe_ci.sh
     - name: Get RosBE
       id: get_rosbe
       uses: actions/cache@v5