Those symbols are not satisfied by any code or dependency of libm. As
result calling cprojf function will always crash on Genode. This crash
can be turned into link time error by adding --no-undefined to LD_OPT.
This patch provides the missing symbols by including isninf.c in libm
build.
Fixes#4299
Replace the FreeBSD libm with OpenLibm, which is easier to port.
OpenLibm is used by Mirage's freestanding Ocaml runtime (sin POSIX).
https://openlibm.org/
Ref #3289