gcc-version

 ❯ arm-none-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=arm-none-eabi-gcc
COLLECT_LTO_WRAPPER=/nix/store/va47si3g9rkmp9z0606b6nx1chpvl023-gcc-arm-embedded-6-2017-q2-update/bin/../lib/gcc/arm-none-eabi/6.3.1/lto-wrapper
Target: arm-none-eabi
Configured with: /tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/src/gcc/configure --target=arm-none-eabi --prefix=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native --libexecdir=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/lib --infodir=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/share/doc/gcc-arm-none-eabi/info --mandir=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/share/doc/gcc-arm-none-eabi/man --htmldir=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/share/doc/gcc-arm-none-eabi/html --pdfdir=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/share/doc/gcc-arm-none-eabi/pdf --enable-languages=c,c++ --enable-plugins --disable-decimal-float --disable-libffi --disable-libgomp --disable-libmudflap --disable-libquadmath --disable-libssp --disable-libstdcxx-pch --disable-nls --disable-shared --disable-threads --disable-tls --with-gnu-as --with-gnu-ld --with-newlib --with-headers=yes --with-python-dir=share/gcc-arm-none-eabi --with-sysroot=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/install-native/arm-none-eabi --build=x86_64-apple-darwin10 --host=x86_64-apple-darwin10 --with-gmp=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/build-native/host-libs/usr --with-mpfr=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/build-native/host-libs/usr --with-mpc=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/build-native/host-libs/usr --with-isl=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/build-native/host-libs/usr --with-libelf=/tmp/jenkins-GCC-6-build_build-toolchain-mac-262_20170621_1498074986/build-native/host-libs/usr --with-host-libstdcxx='-static-libgcc -Wl,-lstdc++ -lm' --with-pkgversion='GNU Tools for ARM Embedded Processors 6-2017-q2-update' --with-multilib-list=rmprofile
Thread model: single
gcc version 6.3.1 20170620 (release) [ARM/embedded-6-branch revision 249437] (GNU Tools for ARM Embedded Processors 6-2017-q2-update)

qmk-build-log

make clean; nix-shell --pure --run "make massdrop/alt:default"
QMK Firmware 0.7.168
Deleting .build/ ... done.
QMK Firmware 0.7.168
Making massdrop/alt with keymap default

arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors 6-2017-q2-update) 6.3.1 20170620 (release) [ARM/embedded-6-branch revision 249437]
Copyright (C) 2016 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.

Compiling: keyboards/massdrop/alt/matrix.c                                                          [OK]
Compiling: keyboards/massdrop/alt/config_led.c                                                      [OK]
Compiling: keyboards/massdrop/alt/keymaps/default/keymap.c                                          [OK]
Compiling: quantum/quantum.c                                                                        [OK]
Compiling: quantum/keymap_common.c                                                                  [OK]
Compiling: quantum/keycode_config.c                                                                 [OK]
Compiling: quantum/debounce/sym_g.c                                                                 [OK]
Compiling: tmk_core/common/arm_atsam/eeprom.c                                                      tmk_core/common/arm_atsam/eeprom.c: In function 'eeprom_read_byte':
tmk_core/common/arm_atsam/eeprom.c:27:24: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
     uintptr_t offset = (uintptr_t)addr;
                        ^
tmk_core/common/arm_atsam/eeprom.c: In function 'eeprom_write_byte':
tmk_core/common/arm_atsam/eeprom.c:32:24: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
     uintptr_t offset = (uintptr_t)addr;
                        ^
cc1: all warnings being treated as errors
 [ERRORS]
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make[1]: *** [tmk_core/rules.mk:380: .build/obj_massdrop_alt_default/common/arm_atsam/eeprom.o] Error 1
make: *** [Makefile:579: massdrop/alt:default] Error 1
Make finished with errors