Draft: Make cuttlefish work with llvmpipe runing with --gpu_mode="guest_swiftshader"

Here are some in-tree changes equivalent to the ones proposed in https://fryzekconcepts.com/notes/android_swrast.html by @Hazematman in particular the ones from mesa/mesa!29344 (merged)

Note: this requires cloning the llvm-project from https://github.com/maurossi/llvm-project into external/llvm-project