Update appveyor.yml

Add Inno setup path to PATH variable.

appveyor.yml

@@ -32,6 +32,7 @@ install:
   - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" set CMAKE_GENERATOR_NAME=Visual Studio 15 2017
   - if "%platform%"=="x64" set CMAKE_GENERATOR_NAME=%CMAKE_GENERATOR_NAME% Win64
   - cmake %CMAKE_DEFINES% -G "%CMAKE_GENERATOR_NAME%"
+  - set PATH=%PATH%;"C:\\Program Files (x86)\\Inno Setup 5"
   - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" iscc packaging\windows-innosetup\script.iss
   
 cache: