Shrink the smallest builds with compile options

[dhalbert]

The trinket_m0 build was running out of space on the latest PR's. It has more in it due to having a DotStar (I think).

These compile options saved about 500 bytes total.

Still left as a possibility is to use a -Os libgcc.a, instead of the current -O2 one, which makes software floating point and various other arithmetic routines noticeably smaller (by at least 1kB or 2kB, I forget which). I have not measured the performance decrease.

[dhalbert]

I am getting paradoxical results on pewpew_m4: the --param max-inline-insns-auto increase is increasing the size rather than decreasing it as on the trinket_m0. Turning this into a draft while I experiment.

[jepler]

This is fine by me. A number of things make debugging tough on these samd21 boards as it is.

[jepler]

Unfortunately, the gains are not uniform. for instance, "meowmeow" no longer fits:

Build meowmeow for de_DE took 17.64s and failed
make: Entering directory '/home/runner/work/circuitpython/circuitpython/ports/atmel-samd'
Use make V=1, make V=2 or set BUILD_VERBOSE similarly in your environment to increase build verbosity.
/usr/bin/../lib/gcc/arm-none-eabi/10.2.1/../../../../arm-none-eabi/bin/ld: build-meowmeow/firmware.elf section `.text' will not fit in region `FLASH_FIRMWARE'
/usr/bin/../lib/gcc/arm-none-eabi/10.2.1/../../../../arm-none-eabi/bin/ld: region `FLASH_FIRMWARE' overflowed by 16 bytes
collect2: error: ld returned 1 exit status
make: *** [Makefile:418: build-meowmeow/firmware.elf] Error 1

[dhalbert]

The single failure in the latest build was a network error, on a build that did not fail before. @jepler, this is ready for re-review.

[jepler]

Thank you