Merge pull request libgit2#4137 from libgit2/ethomson/appveyor

appveyor: don't rewrite the system mingw

Author: Edward Thomson

appveyor.yml

@@ -2,6 +2,7 @@ version: '{build}'
 branches:
   only:
   - master
+  - appveyor
   - /^maint.*/
 environment:
   GITTEST_INVASIVE_FS_STRUCTURE: 1

script/appveyor-mingw.sh

@@ -7,15 +7,17 @@ if [ "$ARCH" = "i686" ]; then
     curl -LsSO http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.2/threads-win32/sjlj/$f
   fi
   7z x $f > /dev/null
-  mv mingw32 /MinGW
+  export PATH=`pwd`/mingw32/bin:$PATH
 else
   f=x86_64-4.9.2-release-win32-seh-rt_v3-rev1.7z
   if ! [ -e $f ]; then
     curl -LsSO http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/4.9.2/threads-win32/seh/$f
   fi
   7z x $f > /dev/null
-  mv mingw64 /MinGW
+  export PATH=`pwd`/mingw64/bin:$PATH
 fi
 cd build
+gcc --version
+cmake --version
 cmake -D ENABLE_TRACE=ON -D BUILD_CLAR=ON .. -G"$GENERATOR"
 cmake --build . --config RelWithDebInfo