Add POSIX times() support

[tenllado]

Describe the bug

Using the newlib libc in Zephyr, the clock() and/or time() functions call the _times_r function which requires the _times function to be supplied, but this function is missing and the compilation fails at link time.

I have tested this while trying to create a lua module for Zephyr. Lua uses both the clock() and the time() function and the compilation fails with the following error:

... zephyr-sdk-0.15.0/arm-zephyr-eabi/arm-zephyr-eabi/lib/thumb/v7e-m/nofp/libc.a(lib_a-timesr.o): in function _times_r': timesr.c:(.text._times_r+0x2): undefined reference to _times'
collect2: error: ld returned 1 exit status

To Reproduce

I prepared a hello_world example available at: https://github.com/tenllado/zephyr_hello_world_lua

The README.md file contains instructions to compile it as a west workspace. The project includes a file src/missing_stubs.c a definition of _times (and also _unlink, which is also missing in Zephyr). If you comment the _times definition you will obtain the error mentioned above.

Expected behavior
Zephyr should be including a definition of the _times function for the newlib libc library.

Impact
The absence of this function prevents the full support of the lua library for the zephyr project.

Environment (please complete the following information):

• OS: Linux
• Toolchain: zephyr-sdk-0.15.0
• Commit SHA: sha for the zephyr project is 8db84cf

[stephanosio]

times is a POSIX function and it is currently not available in the Zephyr POSIX subsystem.

[stephanosio]

Converted to enhancement since newlib cannot map a POSIX function to the POSIX subsystem when it is not implemented by the POSIX subsystem.

[stephanosio]

I did a brief investigation and the ISO C function clock() does depend on the POSIX times(), which is indeed a problem. I will provide a fix such that clock() does not depend on times().

p.s. ISO C time() does not require POSIX times(); instead, it requires _gettimeofday(), which is already provided by the newlib libc-hooks. That aside, the libc hook implementation depending on the POSIX gettimeofday() should not be the case.

[cfriedt]

Just added the modules label, as this blocks the Lua module

[cfriedt]

Just dropping this link here for myself mainly.
https://github.com/zephyrproject-rtos/newlib-cygwin/blob/zephyr-newlib-3.3.0/newlib/libc/time/clock.c

I'm trying to recall how I tied this into sysconf() - perhaps it's not as related as I thought.

[cfriedt]

@stephanosio - do you still want to provide a fix for this, or would #57800 work?

Also, not sure if we should consider this an enhancement or a bug.

[tenllado]

I think that #57800 would fix the problems I am having.