22b8ab15c4
After llvm/clang 13.0.0, the -simplifycfg-dup-ret backend flag is no longer supported. This was part of CLANG_OPT_SMALL, which is only still used for stand/i386/boot2 and stand/i386/isoboot, to achieve the very small binary size required. Luckily clang 13.0.0 does not need any additional flags for this (I get 240 bytes available when building boot2). MFC after: 3 days