> ```
> QMK Firmware 0.7.163
> Making helix/rev2 with keymap default                                                                  [ERRORS]
> In file included from drivers/avr/pro_micro.h:28:0,
>                  from keyboards/helix/rev2/matrix.c:33:
> /gnu/store/gq69j5j0458dcc4jp5ymq62wgnd0mscl-profile/avr/include/avr/pgmspace.h:1456:25: error: unknown type name 'uint_farptr_t'
>  extern size_t strlen_PF(uint_farptr_t src) __ATTR_CONST__; /* program memory can't change */
> ```

I'm not able to reproduce this error. Could you provide the exact steps
you did? Here's what I did.

After applying the patch, drop into an environment with the new avr-toolchain.

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix environment --ad-hoc avr-toolchain
--8<---------------cut here---------------end--------------->8---

Check the version of avr-gcc.

--8<---------------cut here---------------start------------->8---
$ avr-gcc --version

avr-gcc (GCC) 5.5.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
--8<---------------cut here---------------end--------------->8---

Check avr-gcc include paths.

--8<---------------cut here---------------start------------->8---
$ avr-gcc -E -v -

Using built-in specs.
Reading specs from /gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/lib/gcc/avr/5.5.0/device-specs/specs-avr2
COLLECT_GCC=avr-gcc
Target: avr
Configured with: 
Thread model: single
gcc version 5.5.0 (GCC) 
COLLECT_GCC_OPTIONS='-E' '-v' '-specs=device-specs/specs-avr2'
 /gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/libexec/gcc/avr/5.5.0/cc1 -E -quiet -v - -mn-flash=6 -mskip-bug
ignoring nonexistent directory "/gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/lib/gcc/avr/5.5.0/../../../../avr/sys-include"
ignoring nonexistent directory "/gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/lib/gcc/avr/5.5.0/../../../../avr/include"
#include "..." search starts here:
#include <...> search starts here:
 /gnu/store/siwsk54afs7i2g04vmqmxzj69b4rb1rg-profile/avr/include
 /gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/lib/gcc/avr/5.5.0/include
 /gnu/store/cwsiyrcm1c4c25dw0zrgajjnr9mf5k3g-avr-gcc-5.5.0/lib/gcc/avr/5.5.0/include-fixed
End of search list.
^C
--8<---------------cut here---------------end--------------->8---

Navigate to qmk-firmware and clean previous build results.

--8<---------------cut here---------------start------------->8---
$ cd qmk-firmware
$ make clean
--8<---------------cut here---------------end--------------->8---

I'm checking out 0.7.163 and building helix since that's what you seem
to be doing.

--8<---------------cut here---------------start------------->8---
$ git checkout 0.7.163
$ make helix

QMK Firmware 0.7.163
WARNING:
 Python 3 is not installed. It will be required by a future version
 of qmk_firmware.

 Please run util/qmk_install.sh to install all the dependencies QMK requires.

WARNING: Some git submodules are out of date or modified.
 Please consider running make git-submodule.

Making helix/rev2 with keymap default                                                                  [OK]
Making helix/rev2 with keymap edvorakjp                                                                [OK]
Making helix/rev2 with keymap five_rows                                                                [OK]
Making helix/rev2 with keymap five_rows_jis                                                            [OK]
Making helix/rev2 with keymap froggy                                                                   [OK]
Making helix/rev2 with keymap led_test                                                                 [OK]
Making helix/rev2 with keymap xulkal                                                                   [OK]
Making helix/rev2 with keymap yshrsmz                                                                  [OK]
--8<---------------cut here---------------end--------------->8---