compiler/clang: Erase 'no_printf_return_value' prop for clang

[keith-packard]

Clang does not have printf return value optimizations like GCC, so there's no flag to turn them off when building against a non-standard printf implementation (e.g., picolibc without float support).

Signed-off-by: Keith Packard keithp@keithp.com

Fixes #54336

[stephanosio]

@tejlmand Could you take a quick look?

[laurenmurphyx64]

Hi @keith-packard, thanks for the fix! After cherrypicking this onto your picolibc module update PR #54391, I saw the issue was resolved for our XCC-clang target (intel_adsp_ace15_mtpm)!

Unfortunately our CAVS platforms use XCC. Is there a way to also fix this for XCC?

Commit of picolibc: 2097f26ce | cmake: Disable TLS_MODEL and _HAVE_PICOLIBC_TLS without TLS

$ west build -p -b intel_adsp_cavs15 -T tests/kernel/common/kernel.common.picolibc
Building C object modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-malloc_usable_size.c.obj
FAILED: modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-malloc_usable_size.c.obj 
...
xt-xcc ERROR parsing -fno-printf-return-value:  unknown flag

Errored out with these files:

• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-malloc_usable_size.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-mallopt.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-memalign.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-posix_memalign.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-pvalloc.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libc/stdlib/nano-malloc-realloc.c.obj
• modules/picolibc/CMakeFiles/c.dir/newlib/libm/complex/csinh.c.obj

[keith-packard]

xt-xcc ERROR parsing -fno-printf-return-value: unknown flag

Ah, yet another compiler that pretends to be 'just like gcc, but slightly different'. PR #54392 should help here.