Don't call vcvarsall manually

Author: alexcrichton

appveyor.yml

@@ -1,15 +1,11 @@
 environment:
   matrix:
   - TARGET: x86_64-pc-windows-msvc
-    ARCH: amd64
   - TARGET: i686-pc-windows-msvc
-    ARCH: x86
   - TARGET: i686-pc-windows-gnu
-    ARCH: x86
 install:
   - 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"
-  - call "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat" %ARCH%
   - SET PATH=%PATH%;C:\Program Files (x86)\Rust\bin
   - SET PATH=%PATH%;C:\MinGW\bin
   - rustc -V