Not all libc versions have the single precision transcendental functions

[sgjesse]

The LK build fails after 7d94a4d.

out/build-qemu-virt-dartino/out/...mod.o: In function `Native_DoubleAtan':
/mnt/data/b/build/slave/dartino-lk-debug-arm-qemu/build/sdk/out/../src/vm/natives.cc:870: undefined reference to `atanf'
out/build-qemu-virt-dartino/out/...mod.o: In function `Native_DoubleExp':
/mnt/data/b/build/slave/dartino-lk-debug-arm-qemu/build/sdk/out/../src/vm/natives.cc:872: undefined reference to `expf'
out/build-qemu-virt-dartino/out/...mod.o: In function `Native_DoubleLog':
/mnt/data/b/build/slave/dartino-lk-debug-arm-qemu/build/sdk/out/../src/vm/natives.cc:873: undefined reference to `logf'
out/build-qemu-virt-dartino/out/...mod.o: In function `Native_DoubleAtan2':
/mnt/data/b/build/slave/dartino-lk-debug-arm-qemu/build/sdk/out/../src/vm/natives.cc:882: undefined reference to `atan2f'

[travisg]

Pretty easy to add new ones, the math routines in LK are largely added as needed, usually cribbed from FreeBSD or bionic.