bugfix: macOS did not have IPF support (fixes #1126)

The capsimg.so wasn't copied in the bundle, and even if it was, the path was incorrect under macOS.
This implementation is not necessarily according to macOS "standards", since I've copied capsimg.so in the same location the binary is in, but it does work. :)

src/dlopen.cpp

@@ -61,6 +61,9 @@ static amiga_plugin_lookup_function plugin_lookup;
 }
 #endif
 
+#ifdef __MACH__
+#include <mach-o/dyld.h>
+#endif
 UAE_DLHANDLE uae_dlopen_plugin(const TCHAR *name)
 {
 #if defined(AMIBERRY)
@@ -73,7 +76,27 @@ UAE_DLHANDLE uae_dlopen_plugin(const TCHAR *name)
 		return NULL;
 	}
 */
+#ifdef __MACH__
+	char exepath[MAX_DPATH];
+	uint32_t size = sizeof exepath;
+	std::string directory;
+	if (_NSGetExecutablePath(exepath, &size) == 0)
+	{
+		size_t last_slash_idx = string(exepath).rfind('/');
+		if (std::string::npos != last_slash_idx)
+		{
+			directory = string(exepath).substr(0, last_slash_idx);
+		}
+		last_slash_idx = directory.rfind('/');
+		if (std::string::npos != last_slash_idx)
+		{
+			directory = directory.substr(0, last_slash_idx);
+		}
+	}
+	UAE_DLHANDLE handle = uae_dlopen(directory.append("/MacOS/capsimg.so").c_str());
+#else
 	UAE_DLHANDLE handle = uae_dlopen("./capsimg.so");
+#endif // __MACH__
 #elif defined(WINUAE)
 	TCHAR path[MAX_DPATH];
 	_tcscpy(path, name);