waf: gtest: add gtest Waf tool

Tool for building gtest from the submodule.

Tools/ardupilotwaf/gtest.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+"""
+gtest is a Waf tool for test builds in Ardupilot
+"""
+
+def configure(cfg):
+    cfg.env.HAS_GTEST = False
+
+    if cfg.env.STATIC_LINKING:
+        # gtest uses a function (getaddrinfo) that is supposed to be linked
+        # dynamically
+        cfg.msg(
+            'Gtest',
+            'statically linked tests not supported',
+            color='YELLOW',
+        )
+        return
+
+    cfg.start_msg('Checking for gtest submodule')
+    readme = cfg.srcnode.find_resource('modules/gtest/README')
+    if not readme:
+        cfg.end_msg('not initialized', color='YELLOW')
+        return
+    cfg.end_msg('yes')
+
+    cfg.env.HAS_GTEST = True
+
+def build(bld):
+    bld.stlib(
+        source='modules/gtest/src/gtest-all.cc',
+        target='gtest/gtest',
+        includes='modules/gtest/ modules/gtest/include',
+        export_includes='modules/gtest/include',
+        name='GTEST',
+    )