NSIS: quote vlc-cache-gen call

Close #14294

(cherry picked from commit ac3ff888e2db9dab0319ff0715d849572b7a7145)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

extras/package/win32/NSIS/vlc.win32.nsi.in

@@ -209,7 +209,7 @@ ${MementoSection} $Name_Section01 SEC01
 @BUILD_LUA_TRUE@     !insertmacro InstallFolder lua
 
   ; Generate the cache and add it to uninstall.log
-  nsExec::ExecToStack "$INSTDIR\vlc-cache-gen.exe $INSTDIR\plugins"
+  nsExec::ExecToStack '"$INSTDIR\vlc-cache-gen.exe" $INSTDIR\plugins'
   FindFirst $0 $1 "$INSTDIR\plugins\*.dat"
   FileWrite $UninstallLog "plugins\$1$\r$\n"
   FindClose $0