[skip travis] Enable pacman packages caching

Author: in3otd

.appveyor.yml

@@ -15,8 +15,11 @@ skip_commits:
     - .travis.yml
     - '*.md'
 
-#cache:
-#  - C:\msys64\var\cache\pacman\pkg\mingw-w64-x86_64-qt4* -> .appveyor.yml
+cache:
+  # cache pacman packages
+  # max cache size is 1 GB, which should be enough
+  # but in case we could cache only mingw-w64-*-qt4-*
+  - C:\msys64\var\cache\pacman\pkg\ -> .appveyor.yml
 
 install:
 
@@ -43,7 +46,10 @@ install:
   # nevertheless the binary still exists in the repo (for the moment)
   # https://msys2.duckdns.org/repos
   # https://wiki.archlinux.org/index.php/offline_installation_of_packages
-  - bash -lc "cd /var/cache/pacman/pkg && wget http://repo.msys2.org/mingw/$MARCH/mingw-w64-$MARCH-qt4-4.8.7-4-any.pkg.tar.xz && pacman --noconfirm -U mingw-w64-$MARCH-qt4-4.8.7-4-any.pkg.tar.xz"
+  #
+  # download package directly into the local pacman packages directory, cached by AppVeyor
+  # use "no-clobber" option for wget since the file could/should already be in the cache
+  - bash -lc "cd /var/cache/pacman/pkg && wget -nc http://repo.msys2.org/mingw/$MARCH/mingw-w64-$MARCH-qt4-4.8.7-4-any.pkg.tar.xz && pacman --noconfirm -U mingw-w64-$MARCH-qt4-4.8.7-4-any.pkg.tar.xz"
 
   # Set compiler (64bit)
   - set "CC=/c/msys64/mingw%MBITS%/bin/gcc.exe"