ARM and GNU compilers currently are in a mode where they will accept VLAs
in C++ as an extension. IAR does not accept them in C++.
Avoid potential portability surprises by making GCC warn, and
deactivating the extension in ArmCC.
This commit uses the previously introduced feature of generating
configuration data as a C header file rather than as command line macro
definitions. Each toolchain was modified to use prefix headers if
requested, and build_api.py was modified to set up the toolchain's
prefix header content using the data generated by the config system.
Tested by compiling blinky for GCC and ARMCC. I'm having a few issues
with my IAR license currently, but both ARMCC and IAR use the same
`--preinclude` option for prefix headers, so this shouldn't be an issue.
Note that at the moment all exporters still use the previous
configuration data mechanism (individual macro definitions as opposed to
a prefix header). Exporters will be updated in one or more PRs that will
follow.
Laurent Meunier
Mihail Stoyanov
Jimmy Brisson
Sam Grove
Kevin Bracey
Bogdan Marinescu
Martin Kojtal
Vincenzo Frascino
Mihail Stoyanov
Russ Butler