appveyor.yml: try clang

appveyor.yml

@@ -7,15 +7,12 @@ version: "{branch}.{build}"
 environment:
   global:
     GOPATH: c:\gopath
-    # MinGW and Go are preinstalled. Go is already in PATH.
-    PATH: c:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin:%PATH%
+    CC: clang
 
 install:
   - cd c:\gopath\src\github.com\ethereum\go-ethereum
-  - dir c:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin
-  - echo %PATH%
   - go version
-  - gcc --version
+  - clang --version
 
 build_script:
   - go run build\ci.go install