$ xmake f -c -vD -p cross --toolchain=llvm --sdk=/usr/aarch64-linux-gnu
checking for architecture ... none
configure
{
    ccache = true
    theme = default
    diagnosis = true
    toolchain = llvm
    network = public
    clean = true
    sdk = /usr/aarch64-linux-gnu
    arch = none
    ndk_stdcxx = true
    proxy_pac = pac.lua
    builddir = build
    host = linux
    plat = cross
    kind = static
    mode = release
}
$ xmake -r -vD
error: @programdir/core/main.lua:329: @programdir/actions/build/main.lua:146: @programdir/modules/async/runjobs.lua:331: @programdir/core/tool/toolchain.lua:393: @programdir/toolchains/llvm/xmake.lua:64: attempt to index a nil value
stack traceback:
    [@programdir/toolchains/llvm/xmake.lua:64]: