Adding support for Appveyor cache

- Speeds up builds considerably
- Requires stripping out some contents of the gcc arm compiler

appveyor.yml

@@ -1,9 +1,20 @@
 # appveyor file for kiibohd/controller
 # Used to test out the Cygwin builds
 
+# System Build Architecture
 platform:
   - x64
 
+
+# Dependency Cache
+cache:
+  # Cache gcc arm compiler (it's pruned to be under 100 MB)
+  # Invalidate whenever this file is changed
+  - c:/gcc-arm-none-eabi.zip -> appveyor.yml
+
+
+# Build Matrix + Environment Variables
+# NOTE: Only building using 32-bit on a 64-bit system. 64-bit Cygwin should also work fine (no reason to test atm)
 environment:
   global:
     CYG_MIRROR: http://cygwin.uib.no
@@ -11,6 +22,7 @@ environment:
     CYG_ARCH: x86
     CYG_ROOT: C:/cygwin
     WIN_CMAKE: "/cygdrive/c/Program Files (x86)/CMake/bin"
+    ARM_COMPILER_URL: https://launchpad.net/gcc-arm-embedded/5.0/5-2016-q2-update/+download/gcc-arm-none-eabi-5_4-2016q2-20160622-win32.zip
   matrix:
     # Input Club Keyboard Tests
     - SCRIPT_DIR: Keyboards
@@ -34,20 +46,38 @@ environment:
     - SCRIPT_DIR: Bootloader/Builds
       SCRIPT: mk20dx256vlh7.bash
 
+
+# Commands run before cloning git repo
 init:
   - git config --global core.autocrlf input
 
+
+# Setup Build Instance
 install:
   - 'appveyor DownloadFile http://cygwin.com/setup-%CYG_ARCH%.exe -FileName setup.exe'
   - 'setup.exe -qnNdO -R "%CYG_ROOT%" -s "%CYG_MIRROR%" -l "%CYG_CACHE%" -P git -P make -P python3 -P ctags -P tree -P p7zip'
   - '%CYG_ROOT%/bin/bash -lc "cygcheck -dc cygwin"'
   - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\"/%SCRIPT_DIR% && export wincmake_path=\"%WIN_CMAKE%\" && which cmake"'
-  - 'appveyor DownloadFile https://launchpad.net/gcc-arm-embedded/5.0/5-2016-q2-update/+download/gcc-arm-none-eabi-5_4-2016q2-20160622-win32.zip -FileName gcc-arm-none-eabi.zip'
+  - '%CYG_ROOT%/bin/bash -lc "ls -l /cygdrive/c"'
+  # Only download if cache is missing
+  - if not exist c:/gcc-arm-none-eabi.zip appveyor DownloadFile %ARM_COMPILER_URL% -FileName c:/gcc-arm-none-eabi.zip
+  # Always try to strip out the unnecessary binaries
+  # Necessary, so we can fit gcc-arm-none-eabi.zip into the dependency cache
+  # For ARM Cortex-M4 we only need armv7e-m (also supports Cortex-M7)
+  # https://en.wikipedia.org/wiki/ARM_architecture#Cores
+  - 7z d c:/gcc-arm-none-eabi.zip "armv6*" -r
+  - 7z d c:/gcc-arm-none-eabi.zip "armv7-m*" -r
+  - 7z d c:/gcc-arm-none-eabi.zip "armv7-ar*" -r
+  - 7z d c:/gcc-arm-none-eabi.zip "armv8*" -r
+  - 7z d c:/gcc-arm-none-eabi.zip "*.html" -r
   - dir
   - cmake --version
 
+
+# Build Commands
 build_script:
-  - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && 7z x -o/ gcc-arm-none-eabi.zip"'
+  - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && du -sh /cygdrive/c/gcc-arm-none-eabi.zip"'
+  - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && 7z x -o/ /cygdrive/c/gcc-arm-none-eabi.zip"'
   - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && pwd"'
   - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && tree"'
   - '%CYG_ROOT%/bin/bash -lc "cd \"$OLDPWD\" && cmake --version"'