689dfe8004
Firstly, BUILD_CC_ARCH is included in BUILD_CC (hence why we actually need a BUILD_CC wrapper because it produces the space), so its redundant (now with the wrapper using BUILD_CC). The RUST_BUILD_CFLAGS variable doesn't need to be exported since its not actually used by rustc/gcc-rs/cargo. Since its redundant and doesn't need to be exported remove it and simplify.