This commit updates the Zephyr build system to support specifying
advanced floating-point compilation options derived from the newly
introduced unified floating-point configurations.
The following changes are introduced by this commit:
1. Specify architecture floating-point option to the `-mcpu` flag.
2. Specify floating-point unit (FPU) type using the `-mfpu` flag.
Note that the `-march` flag is not specified separately because the
`-mcpu` flag provides more detailed architecture options and this
makes the `-march` flag redundant.
Signed-off-by: Stephanos Ioannidis <root@stephanos.io>