android: fix llvmpipe build rules

llvmpipe driver name needs to be added to the list triggering MESON_GEN_LLVM_STUB := true
due to swrast driver name being an invalid gallium driver

swrast driver name is still used for lavapipe vulkan driver

Fixes: a3909092 ("meson: drop deprecated `swrast` alias for softpipe+llvmpipe")
Backport-to: 25.1
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35121>
1 file changed