SDL: tests: build tests with C99 standard by default

SDL Commits
1 
From 0e96cbd8ceebddb9dca9060e17a1e8913053789f Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Fri, 5 Dec 2025 16:29:47 +0100
Subject: [PATCH] tests: build tests with C99 standard by default

---
 test/CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 8256f4a9312a4..8b93e754e558d 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -4,6 +4,10 @@
 
 cmake_minimum_required(VERSION 3.16)
 
+if(NOT DEFINED CMAKE_C_STANDARD)
+    set(CMAKE_C_STANDARD 99)
+endif()
+
 set(SDL3_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/..")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/../cmake")