configure: Remap -L to -libpath for msvc

This allows using libraries that are detected via pkg-config with
msvc. (The libraries themselves may have to be built with MSVC
though.)
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -2702,6 +2702,7 @@ msvc_common_flags(){
             -lavifil32)           echo vfw32.lib ;;
             -lavicap32)           echo vfw32.lib user32.lib ;;
             -l*)                  echo ${flag#-l}.lib ;;
+            -L*)                  echo -libpath:${flag#-L} ;;
             *)                    echo $flag ;;
         esac
     done