appveyor.yml: Add Cygwin build and tests (#2006)

appveyor.yml

@@ -23,6 +23,7 @@ environment:
       configuration: Debug
       vcvarsall_platform: x64
       PlatformToolset: v120
+      cygwin_build: yes
     - VisualStudioVersion: 12.0
       platform: x64
       configuration: Release
@@ -85,6 +86,7 @@ test_script:
   - python -m pytest test-helloworld.py
   - python -m pytest test-inline-suppress.py
   - python -m pytest test-suppress-syntaxError.py
+  - 'IF defined cygwin_build C:\cygwin64\bin\bash -e -l -c "cd /cygdrive/c/projects/cppcheck && make clean && make -j 2 && make test && make checkcfg"'
 
 artifacts:
   - path: bin