gtest: Add a testcase wrapper for handling tmpdirs

This makes it trivial to have a pristine temp directory on every test
case execution. Just derive from the provided class.

Change-Id: I5355914cdedc482eddd0749a9ccc10fc93de6571
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/include-gtest/meson.build b/include-gtest/meson.build
new file mode 100644
index 0000000..dfba348
--- /dev/null
+++ b/include-gtest/meson.build
@@ -0,0 +1,5 @@
+stdplus_gtest_headers = include_directories('.')
+
+install_headers(
+  'stdplus/gtest/tmp.hpp',
+  subdir: 'stdplus')