AppVeyor has MSYS2 installed by default now!

appveyor.yml

 environment:
-  global:
-    MSYS2_BASEVER: 20150512
   matrix:
   - TARGET: x86_64-pc-windows-gnu
-    MSYS2_ARCH: x86_64
     MSYS2_BITS: 64
-    MSYSTEM: MINGW64
   - TARGET: i686-pc-windows-gnu
-    MSYS2_ARCH: i686
     MSYS2_BITS: 32
-    MSYSTEM: MINGW32
   - TARGET: x86_64-pc-windows-msvc
   - TARGET: i686-pc-windows-msvc
 install:
-  - ps: ci\msys2.ps1
   - ps: Start-FileDownload "https://static.rust-lang.org/dist/rust-nightly-${env:TARGET}.exe"
   - rust-nightly-%TARGET%.exe /VERYSILENT /NORESTART /DIR="C:\Program Files (x86)\Rust"
   - SET PATH=%PATH%;C:\Program Files (x86)\Rust\bin
-  - if defined MSYS2_BITS set PATH=%PATH%;%CD%\msys2\mingw%MSYS2_BITS%\bin
+  - if defined MSYS2_BITS set PATH=%PATH%;C:\msys64\mingw%MSYS2_BITS%\bin
   - rustc -V
   - cargo -V
 

ci/msys2.ps1

-# Installs MSYS2 on AppVeyor builders
-
-If (!${env:MSYS2_ARCH}) {
-  Exit 0
-}
-
-Start-FileDownload `
-  ("http://kent.dl.sourceforge.net/project/msys2/Base/" + `
-    $env:MSYS2_ARCH + "/msys2-base-" + $env:MSYS2_ARCH + "-" + `
-    $env:MSYS2_BASEVER + ".tar.xz") `
-  -FileName "msys2.tar.xz"
-
-7z x msys2.tar.xz
-7z x msys2.tar > $nul
-Move-Item ("msys" + $env:MSYS2_BITS) msys2
-.\msys2\usr\bin\bash.exe -lc ""
-.\msys2\usr\bin\bash.exe -lc `
-  ("for i in {1..3}; do " + `
-      "pacman --noconfirm -Suy mingw-w64-"+ $env:MSYS2_ARCH + "-gcc " + `
-        "&& break || sleep 15; " + `
-  "done")
-.\msys2\autorebase.bat