Currently, `PICOLIBC_SUPPORTED` could be enabled even when
neither the toolchain has picolibc nor the picolibc module is
present, this can be the case when Zephyr is built with
external toolchain (non-Zephyr SDK) + external build system
where PICOLIBC module doesn't exist.
Fix this by having `PICOLIBC_SUPPORTED` depends on either
toolchain OR module, while taking the libc++ into
consideration.
Here's the full logic table of when the PICOLIBC should
be marked as supported.
libc++ TOOLCHAIN MODULE PICOLIBC_SUPPORTED
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 1
1 1 1 1
Co-authored-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
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