Fix cabal rename error.

See #110. [skip ci]

.appveyor.yml

@@ -8,7 +8,7 @@ install:
     - bash -lc "mkdir /usr/local"
     - bash -lc "mkdir /usr/local/bin"
     - bash -lc "curl -LsS https://www.haskell.org/cabal/release/cabal-install-1.22.0.0/cabal-1.22.0.0-i386-unknown-mingw32.tar.gz | tar -xz -C /usr/local/bin"
-    - ren C:\msys64\usr\local\bin\cabal-1.22.0.0-i386-unknown-mingw32.exe C:\msys64\usr\local\bin\cabal.exe
+    - bash -lc "mv /usr/local/bin/cabal-1.22.0.0-i386-unknown-mingw32.exe /usr/local/bin/cabal.exe"
     - bash -lc "cabal update"
     - bash -lc "cabal install -j --prefix=/usr/local alex happy"
     - bash -lc "git clone --recursive git://git.haskell.org/ghc.git /home/ghc"