No functionality change is intended with this commit, it just consolidates
the separate implementations of GC helper code to the lib/utils/ directory
as a general set of helper functions useful for any port. This reduces
duplication of code, and makes it easier for future ports or embedders to
get the GC implementation correct.
Ports should now link against gchelper_native.c and either gchelper_m0.s or
gchelper_m3.s (currently only Cortex-M is supported but other architectures
can follow), or use the fallback gchelper_generic.c which will work on
x86/x64/ARM.
The gc_helper_get_sp function from gchelper_m3.s is not really GC related
and was only used by cc3200, so it has been moved to that port and renamed
to cortex_m3_get_sp.
This is an extremely minimal port to the NXP i.MX RT, in the style of the
SAMD port It's largely based on the TinyUSB mimxrt implementation, using
the NXP SDK. It currently supports the Teensy 4.0 board with a REPL over
the USB-VCP interface.
This commit also adds the NXP SDK submodule (also from TinyUSB) to
lib/nxp_driver.
Note: if you already have the tinyusb submodule initialized recursively you
will need to run the following as the tinyusb sub-submodules have been
rearranged (upstream):
git submodule deinit lib/tinyusb
rm -rf .git/modules/lib/tinyusb
git submodule update --init lib/tinyusb
