[wf-pacman] Add hook to relocate binaries and libraries with patchelf

[asiekierka]

On Linux, we use patchelf to make toolchain binaries and libraries use the toolchain-provided build of musl libc, like so:

wf_runtime_patchelf() {
        if [ "$WF_USE_MUSL" == "true" ]; then
                patchelf --set-rpath "$WF_PATH/lib" "$1"
                # Setting an interpreter is supported only on executables.
                # For libraries, ignore the failure.
                patchelf --set-interpreter "$WF_PATH/lib/ld-musl-$CARCH.so.1" "$1" || true
        fi
}

As a limitation, this hardcodes /opt/wonderful as the location for ld-musl.so.1. Fixing this requires doing a few things:

• packaging patchelf as wf-patchelf on Linux (statically built!),
• writing a Pacman hook that iterates over $WONDERFUL_TOOLCHAIN on installs/updates and patches all binaries/host libraries found.