Windows builds fail with LTO in some (slow) machines

[carlescufi]

We are seeing the following:

west build -b nrf54l15dk/nrf54l15/cpuapp samples\hello_world -- -DCONFIG_LTO=y -DCONFIG_ISR_TABLES_LOCAL_DECLARATION=y
[snip]
zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: cannot find C:\Users\...\AppData\Local\Temp\ccqKSDAR.ltrans0.ltrans.o: No such file or directory
zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd.exe: cannot find C:\Users\...\AppData\Local\Temp\ccqKSDAR.ltrans1.ltrans.o: No such file or directory

Changing all instances of -flto=auto to -flto=1 fixes the issue, so this is clearly a multithreading issue.
Also, this does not happen with GNU Arm Embedded, so perhaps we should take a look at how things are compiled there.

There's some precedent here:
Nuitka/Nuitka#1768 (comment)

@stephanosio I see that there's a difference between building the toolchain with win32-threads or posix-threads, which one do we use currently?