Unable to Build 1.2.6 on OSX Sierra 10.12.6

I’m attempting to follow the instructions (found in install.md) to build aseprite 1.2.6 on macOS. The Skia build successfully completes, but when I attempt to compile Aseprite I get a single error:

> CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
> Please set them or make sure they are set and tested correctly in the CMake files:
>     linked by target "she" in directory [local path]/Aseprite-v1.2.6-Source/src/she

I’m using the following command to build Skia:

mkdir $HOME/deps
cd $HOME/deps
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
git clone https://github.com/aseprite/skia.git
export PATH="${PWD}/depot_tools:${PATH}"
cd skia
git checkout aseprite-m62
python tools/git-sync-deps
gn gen out/Release --args="is_official_build=true skia_use_system_expat=false skia_use_system_icu=false skia_use_system_libjpeg_turbo=false skia_use_system_libpng=false skia_use_system_libwebp=false 
ninja -C out/Release

and the following build command to build Aseprite:

cd aseprite
mkdir build
cd build
cmake \
  -DCMAKE_OSX_SYSROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk \
  -DSKIA_DIR=$HOME/deps/skia \
  -DWITH_HarfBuzz=OFF \
  -G Ninja \
ninja aseprite

Let me know if any more information is required.

Aseprite 1.2.6 and OSX Sierra 10.12.6