Update appveyor.yml

Author: SlavaRa

appveyor.yml

@@ -33,7 +33,7 @@ after_build:
 - 7z a %PLUGIN_NAME%.zip $(BaseDir)\
 - mv %PLUGIN_NAME%.zip %PLUGIN_NAME%.fdz
 - cd %PLUGIN_PATH%
-- md5sum %APPVEYOR_BUILD_FOLDER%\%PLUGIN_NAME%.fdz > checksum.md5
+- md5sum %APPVEYOR_BUILD_FOLDER%/%PLUGIN_NAME%.fdz > checksum.md5
 - cat checksum.md5
 - sed -e "s/ .*//" checksum.md5 > checksum.tmp.md5 && mv checksum.tmp.md5 checksum.md5
 - set /p CHECKSUM=<checksum.md5