Factor out platform checks into platform.h header

This functionality will be used in compositortest.cc in the next commit.

BUG=none
TEST=none

Change-Id: Ifcb9f91d4da914a0bb519514464a599d8cbce957
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/glbench/+/5416276
Commit-Queue: ChromeOS Auto Retry <chromeos-auto-retry@chromeos-bot.iam.gserviceaccount.com>
Auto-Submit: Matt Turner <msturner@google.com>
Tested-by: Matt Turner <msturner@google.com>
Reviewed-by: Ilja Friedel <ihf@chromium.org>

src/platform.h

diff --git a/src/platform.h b/src/platform.h
new file mode 100644
index 0000000..0229aa7
--- /dev/null
+++ b/src/platform.h
@@ -0,0 +1,17 @@
+// Copyright 2024 The ChromiumOS Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BENCH_GL_PLATFORM_H_
+#define BENCH_GL_PLATFORM_H_
+
+#define ID_PLATFORM_GLX 1
+#define ID_PLATFORM_X11_EGL 2
+#define ID_PLATFORM_NULL 3
+
+#define CONCAT(a, b) a##b
+#define PLATFORM_ID(x) CONCAT(ID_, x)
+#define PLATFORM_ENUM(x) CONCAT(WAFFLE_, x)
+#define THIS_IS(x) PLATFORM_ID(x) == PLATFORM_ID(PLATFORM)
+
+#endif  // BENCH_GL_PLATFORM_H_

src/waffle_stuff.cc

diff --git a/src/waffle_stuff.cc b/src/waffle_stuff.cc
index 3f7c7a7..d162c35 100644
--- a/src/waffle_stuff.cc
+++ b/src/waffle_stuff.cc
@@ -8,6 +8,7 @@
 
 #include <stdio.h>
 #include "main.h"
+#include "platform.h"
 #include "utils.h"
 #include "waffle_stuff.h"
 
@@ -28,15 +29,6 @@
 #define GL_API WAFFLE_CONTEXT_OPENGL_ES2
 #endif
 
-#define ID_PLATFORM_GLX 1
-#define ID_PLATFORM_X11_EGL 2
-#define ID_PLATFORM_NULL 3
-
-#define CONCAT(a, b) a##b
-#define PLATFORM_ID(x) CONCAT(ID_, x)
-#define PLATFORM_ENUM(x) CONCAT(WAFFLE_, x)
-#define THIS_IS(x) PLATFORM_ID(x) == PLATFORM_ID(PLATFORM)
-
 #if THIS_IS(PLATFORM_GLX)
 #include "waffle_glx.h"
 #elif THIS_IS(PLATFORM_X11_EGL)