win-capture: Fix mingw compiler warnings

plugins/win-capture/game-capture.c

@@ -604,7 +604,7 @@ static inline bool hook_direct(struct game_capture *gc,
 	CloseHandle(process);
 
 	if (ret != 0) {
-		warn("hook_direct: inject failed: %ld", ret);
+		warn("hook_direct: inject failed: %d", ret);
 		return false;
 	}
 

plugins/win-capture/inject-helper/inject-helper.c

@@ -94,6 +94,8 @@ static int inject_helper(wchar_t *argv[], const wchar_t *dll)
 		: inject_library_full(id, dll);
 }
 
+#define UNUSED_PARAMETER(x) ((void)(x))
+
 int main(int argc, char *argv_ansi[])
 {
 	wchar_t dll_path[MAX_PATH];
@@ -119,5 +121,6 @@ int main(int argc, char *argv_ansi[])
 	}
 	LocalFree(argv);
 
+	UNUSED_PARAMETER(argv_ansi);
 	return ret;
 }

plugins/win-capture/inject-library.c

@@ -23,7 +23,7 @@ int inject_library_obf(HANDLE process, const wchar_t *dll,
 	bool success = false;
 	size_t written_size;
 	DWORD thread_id;
-	HANDLE thread;
+	HANDLE thread = NULL;
 	size_t size;
 	void *mem;