Revert "Bit of a WAG to hopefully find libstdc++ during build"

This reverts commit e4b2ccb.

https://discord.com/channels/763778740345765900/764131312117743656/1330986352296071270

Discussion with @endill

Author: mattgodbolt

build/build.sh

@@ -408,7 +408,6 @@ df -h /
 # Setup build directory and build configuration
 mkdir -p "${BUILD_DIR}"
 cd "${BUILD_DIR}"
-export LD_LIBRARY_PATH="/opt/compiler-explorer/gcc-${GCC_VERSION}/lib64"
 cmake \
     -G "Ninja" "${ROOT}/llvm-project/llvm" \
     -DLLVM_ENABLE_PROJECTS="${LLVM_ENABLE_PROJECTS}" \