libobs: Fix duplicate symbol resolution for obs plugins

By default duplicate non-static symbols loaded by dynamic libraries are
de-duplicated by the dynamic library loader. This can lead to issues
with statically linked libraries inside obs plugins if the symbols
share their signature: Whichever plugin is loaded first gets to "set"
the symbol (which can become problematic especially for C++ template
functions).

Using RTLD_LOCAL ensures that all symbols are hidden and can only be
explicitly loaded using dlsym() which avoids this issue.

Unfortunately due to the way scripting works in obs-studio, Python
still needs to be loaded with RTLD_GLOBAL, hence the branch in the fix.

libobs/util/platform-nix.c

@@ -83,7 +83,13 @@ void *os_dlopen(const char *path)
 		dstr_cat(&dylib_name, ".so");
 
 #ifdef __APPLE__
-	void *res = dlopen(dylib_name.array, RTLD_LAZY | RTLD_FIRST);
+	int dlopen_flags = RTLD_LAZY | RTLD_FIRST;
+	if (dstr_find(&dylib_name, "Python")) {
+		dlopen_flags = dlopen_flags | RTLD_GLOBAL;
+	} else {
+		dlopen_flags = dlopen_flags | RTLD_LOCAL;
+	}
+	void *res = dlopen(dylib_name.array, dlopen_flags);
 #else
 	void *res = dlopen(dylib_name.array, RTLD_LAZY);
 #endif