Switch libm to libcrt.builtins

After switching libm from libgcc to libcrt.builtins, some of the symbols
are no longer getting included in libm, causing the compiler to complain
about missing symbols from the version script. Explicitly export them in
libc (since libm depends on libc).

Bug: 122993571
Test: m checkbuild
Test: bionic-unit-tests
Change-Id: Ie91765874d20df605f557b1a8c4236619553c549