radeonsi: try to fix meson

radeonsi: try to fix meson

This is not fully tested. Meson can't link LLVM even though automake can.

PATH=/usr/llvm/x86_64-linux-gnu/bin:$PATH meson build/ -Dgallium-va=false \
    -Dplatforms=x11,drm -Dgallium-drivers=radeonsi -Ddri-drivers= \
    -Dgallium-omx=disabled -Dgallium-xvmc=false -Dgles1=false \
    -Dtexture-float=true -Dvulkan-drivers=

src/gallium/auxiliary/libgallium.a(gallivm_lp_bld_misc.cpp.o):
(.data.rel.ro._ZTI26DelegatingJITMemoryManager[_ZTI26DelegatingJITMemoryManager]+0x10):
undefined reference to `typeinfo for llvm::RTDyldMemoryManager'

Acked-by: Timothy Arceri <tarceri@itsqueeze.com>