Mesa's radeonsi/radv AMD-GPU drivers require the LLVM 'amdgpu' codegen backend
(dependency('llvm', modules: [... amdgpu ...])). llvm21 built X86 only, so the
host llvm-config the mesa build reads reported amdgpu(missing). Add AMDGPU to
LLVM_TARGETS_TO_BUILD (X86;AMDGPU per the amd64-only policy — AMDGPU is a GPU
backend, not a second CPU platform). This is the redox-target LLVM whose libs
mesa links AND the source of the prefix clang-install host LLVM. NB: the
~/.redoxer toolchain host llvm-config (a provisioned prebuilt) still needs the
rebuilt AMDGPU host-LLVM propagated into it (follow-up).
vasilito
5d087d63bc