Otherwise the different instances of _start_c from each compilation unit
will lead to linker errors:
/usr/bin/ld: /tmp/ccSNvRqs.o: in function `_start_c':
nolibc-test-foo.c:(.text.nolibc_memset+0x9): multiple definition of `_start_c'; /tmp/ccG25101.o:nolibc-test.c:(.text+0x1ea3): first defined here