[appveyor] use cmake to build

Author: xoviat

.appveyor.yml

@@ -20,5 +20,5 @@ build_script:
   - cd build
   - set "PATH=%cd%\bin;%PATH%"
   - call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" amd64
-  - cmake -G "NMake Makefiles" -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_Fortran_COMPILER=flang -DCMAKE_BUILD_TYPE=Release ..
-  - nmake VERBOSE=1
+  - cmake -G "NMake Makefiles" -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_Fortran_COMPILER=flang -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_BUILD_TYPE=Release ..
+  - cmake --build .