Allow building against cosmopolitan libc #274

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	30m 5s
ci (a6osx, macos-12)	13m 50s
ci (ta6osx, macos-12)	17m 45s
ci (arm64osx, macos-14)	8m 54s
ci (tarm64osx, macos-14)	10m 32s
ci (i3le, ubuntu-22.04)	11m 56s
ci (ti3le, ubuntu-22.04)	14m 38s
ci (a6le, ubuntu-22.04)	9m 18s
ci (ta6le, ubuntu-22.04, CFLAGS+=-std=gnu89)	12m 15s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 33s
ci (i3nt, windows-2022, vs)	11m 12s
ci (ti3nt, windows-2022, vs)	13m 48s
ci (a6nt, windows-2022, vs)	11m 35s
ci (ta6nt, windows-2022, vs)	14m 59s
ci (ta6nt, windows-2022, gcc, CFLAGS+=-std=gnu89)	13m 47s
	3h 23m 7s

Provide feedback