Add missing path separator in Safari Extensions table generator

[Micah-Kolide]

Fixes #8210

Simple one line change to correct the file path(s) genSafariSandboxedExtensions iterates over. I'm unsure if listDirectoriesInDirectory previously returned the path with the ending separator, but it currently does not seem to do so. Since kSafariAppExtensionsPlistPath is isolated I decided to just add the path separator instead of digging further.

Example:

Pre PR:

/Applications/AdBlock.appContents/PlugIns/%.appex/Contents/Info.plist

Post PR:

/Applications/AdBlock.app/Contents/PlugIns/%.appex/Contents/Info.plist

[directionless]

Thank you for trackin this down!

Fix seems fine, though I wonder if https://www.boost.org/doc/libs/1_34_0/libs/filesystem/doc/index.htm has anything clever in there.

[zwass]

Agreed that the boost filesystem type could handle this, but it seems unnecessary to me when dealing with a constant -- let's just give it the slash it needs.