Meta: Copy libstdc++ into the disk image

With this, we can now compile C++ programs with the LLVM port without
having to jump through hooks to build libc++ because it can't be
cross-compiled with our GNU toolchain.

Meta/build-root-filesystem.sh

@@ -56,6 +56,8 @@ if [ "$SERENITY_TOOLCHAIN" = "Clang" ]; then
     $CP -r "$TOOLCHAIN_DIR"/include/"$SERENITY_ARCH"-pc-serenity/c++ mnt/usr/include/"$SERENITY_ARCH"-pc-serenity
 elif [ "$SERENITY_ARCH" != "aarch64" ]; then
     $CP "$SERENITY_SOURCE_DIR"/Toolchain/Local/"$SERENITY_ARCH"/"$SERENITY_ARCH"-pc-serenity/lib/libgcc_s.so mnt/usr/lib
+    $CP "$SERENITY_SOURCE_DIR"/Toolchain/Local/"$SERENITY_ARCH"/"$SERENITY_ARCH"-pc-serenity/lib/libstdc++.a mnt/usr/lib
+    $CP -r "$SERENITY_SOURCE_DIR"/Toolchain/Local/"$SERENITY_ARCH"/"$SERENITY_ARCH"-pc-serenity/include/c++ mnt/usr/include
 fi
 
 # If umask was 027 or similar when the repo was cloned,