I'm still not using github for the projects
those functions not available in toolchains, you have to find it's source
and build an object module from it.
maybe this
cexpf is the right one, from glibc.
sometimes you have additional dependecies from those new functions, so you have to build them aswell.
#1) some compiler refused the weak_alias statement - so you have to remove that sections,
and adjust the lines above. so the object file provides the correct __function.