stage2: Force Clang to use LLVM's assembler for SPARC targets
stage2: Force Clang to use LLVM's assembler for SPARC targets

This change allows cross-compiling C code for SPARC, if you hit any
error with the internal assembler please open a ticket.

zig-lang/zig,zig-lang/zig,zig-lang/zig,andrewrk/zig,andrewrk/zig