Fix "standalone pacman" compile errors with gcc >9.2.1

[NotherNgineer]

Since the introduction of standalone pacman app in PR #2145, it's been impossible to build Mayhem firmware with any compiler version above 9.2.1. (Yes I realize that 9.2.1 is the "official" build version but I prefer the warning message versus strange compiler errors below.)

This command line switch resolves the issue, and is already being used in the cmake file when building applications so there should be no adverse affects.

Thanks to @Brumi-2021 for this fix.

BTW, this is what the errors look like without this fix:
/opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-writer.o): in function _write_r':
writer.c:(.text._write_r+0x10): undefined reference to _write' /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-closer.o): in function _close_r':
closer.c:(.text._close_r+0xc): undefined reference to _close' /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-fstatr.o): in function _fstat_r':
fstatr.c:(.text._fstat_r+0xe): undefined reference to _fstat' /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-isattyr.o): in function _isatty_r':
isattyr.c:(.text._isatty_r+0xc): undefined reference to _isatty' /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-lseekr.o): in function _lseek_r':
lseekr.c:(.text._lseek_r+0x10): undefined reference to _lseek' /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: /opt/build/armbin/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libg_nano.a(lib_a-readr.o): in function _read_r':
readr.c:(.text._read_r+0x10): undefined reference to _read' collect2: error: ld returned 1 exit status make[2]: *** [firmware/standalone/pacman/CMakeFiles/pacman_app.elf.dir/build.make:114: firmware/standalone/pacman/pacman_app.elf] Error 1 make[1]: *** [CMakeFiles/Makefile2:2095: firmware/standalone/pacman/CMakeFiles/pacman_app.elf.dir/all] Error 2

[NotherNgineer]

This same fix is also in PR #2224 but that PR is currently in Draft state.

[gullradriel]

So what's the plan ?
Which one first ?

[gullradriel]

Good to go

[gullradriel]

Hmm as the other one is a draft, we will ask @Brumi-2021 to fix his branch if a conflict arise.

[Brumi-2021]

Do not worry , as it is already merged here ,
I will remove that part from my yesterday's DRAFT PR .
And at the same time , I will also re-activate again the error when the compiled binary size is > 1MB flash .
Thanks to all checkers