Updated AppVeyor config to the source-based mechanism.

Author: LeStahL

.appveyor.yml

@@ -17,15 +17,12 @@ install:
         Invoke-WebRequest "https://web.archive.org/web/20200502121517/https://www.steinberg.net/sdk_downloads/vstsdk366_27_06_2016_build_61.zip" -OutFile "vstsdk.zip"
         Expand-Archive "vstsdk.zip" "C:\tmp"
       }
-      if (-Not (Test-Path "C:\tmp\Monad.FLParser.dll")) {
-        Invoke-WebRequest "https://github.com/LeStahL/FLParser/releases/download/compatibility-20.9/Monad.FLParser.dll" -OutFile "C:\tmp\Monad.FLParser.dll"
-      }
 
 build_script:
   # build native code/tests
   - mkdir build
   - cd build
-  - cmake -DCMAKE_GENERATOR_PLATFORM=%PLATFORM% -DVSTSDK3_DIR="C:/tmp/VST3 SDK" -DMONAD_FL_PARSER_DIR="C:/tmp/" ..
+  - cmake -DCMAKE_GENERATOR_PLATFORM=%PLATFORM% -DVSTSDK3_DIR="C:/tmp/VST3 SDK" -DDOWNLOAD_MONAD_FL_PARSER=ON -DMONAD_FL_PARSER_DIR="C:/tmp/Monad.FLParser" ..
   - msbuild /v:minimal /nologo WaveSabre.sln
   - msbuild /v:minimal /nologo /property:Configuration="MinSizeRel" WaveSabre.sln
   - cd ..