$ cc -fstrength-reduce -nostdinc -m32 -nostdlib -fno-builtin \ -nostartfiles -nodefaultlibs -I. -ggdb -I. -c -o boot.o boot.S clang: warning: optimization flag '-fstrength-reduce' is not supported clang: warning: argument unused during compilation: '-nostartfiles' boot.S:21:23: error: unexpected token in '.section' directive