sdl12-compat: macOS: fall back to @executable_path, _just in case_ @loader_path isn't right.

SDL Commits
1 
From 7157c3dbcc4c1bd89e89e77866435095d2c053d1 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 1 Jun 2021 16:05:08 -0400
Subject: [PATCH] macOS: fall back to @executable_path, _just in case_
 @loader_path isn't right.

---
 src/SDL12_compat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 6967484..623155e 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -902,6 +902,8 @@ static char loaderror[256];
         static const char * const dylib_locations[] = {
             "@loader_path/" SDL20_LIBNAME, /* MyApp.app/Contents/MacOS/libSDL2-2.0.0.dylib */
             "@loader_path/../Frameworks/" SDL20_FRAMEWORK, /* MyApp.app/Contents/Frameworks/SDL2.framework */
+            "@executable_path/" SDL20_LIBNAME, /* MyApp.app/Contents/MacOS/libSDL2-2.0.0.dylib */
+            "@executable_path/../Frameworks/" SDL20_FRAMEWORK, /* MyApp.app/Contents/Frameworks/SDL2.framework */
             NULL,  /* /Users/username/Library/Frameworks/SDL2.framework */
             "/Library/Frameworks" SDL20_FRAMEWORK, /* /Library/Frameworks/SDL2.framework */
             SDL20_LIBNAME  /* oh well, anywhere the system can see the .dylib (/usr/local/lib or whatever) */