Solved!
In the previous step, I learned that the **cross-compile arguments MUST be on
the command line** , they cannot be in `nim.cfg`. Combine this with the
following.
The next clue in this puzzle was to try the arm_sandbox project on another
Windows10 machine . . . and it worked. I narrowed the problem to the version of
the arm-none-eabi-gcc toolchain I used to cross-compile.
**A version of arm-none-eabi-gcc circa 2016 is what works, while a recent
release circa 2023 is what fails.**
Works:
arm-none-eabi-gcc --version
arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 5.4.1 20160609
(release) [ARM/embedded-5-branch revision 237715]
Copyright (C) 2015 Free Software Foundation, Inc.
Run
Fails:
arm-none-eabi-gcc.exe (Arm GNU Toolchain 13.2.rel1 (Build arm-13.7)) 13.2.1
20231009
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Run
bisecting the versions of toolchains to find where the incompatibility was
introduced is an exercise for the reader.
