SDL: add-source-to-projects.pl: Fix adding files in the base src dir.

From 8745a9949b360a4165047ad0b1ee99380a3c09e5 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 9 Oct 2023 19:15:54 -0400
Subject: [PATCH] add-source-to-projects.pl: Fix adding files in the base src
 dir.

---
 build-scripts/add-source-to-projects.pl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/build-scripts/add-source-to-projects.pl b/build-scripts/add-source-to-projects.pl
index 4530e92dfa22..6d703dc36b00 100755
--- a/build-scripts/add-source-to-projects.pl
+++ b/build-scripts/add-source-to-projects.pl
@@ -438,6 +438,7 @@ sub process_visualstudio {
         $filter = lc(dirname($addpath));
         $filter =~ s/\Asrc\///; # there's no filter for the base "src/" dir, where SDL.c and friends live.
         $filter =~ s/\//\\/g;
+        $filter = '' if $filter eq 'src';
 
         if ($filter ne '') {
             # see if the filter already exists, otherwise add it.