Small Cortex-M4 toolchain tweaks
Small Cortex-M4 toolchain tweaks

Updates Cortex-M4 toolchain to use nano.specs and soft FPU.

Change-Id: I7f4d97bb428b38d90cae9041487460e6c2eed184

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed