meson: Make googletest vendorable

This is a quality of life improvement so that users trying to work with
the project don't need to have an external install of the googletest
dependency for the tests to build.

Change-Id: I44b4cbae14c5006eaef0a5b42a1f6b753b07b405
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meson.build b/meson.build
index ae55b6a..d69fee3 100644
--- a/meson.build
+++ b/meson.build
@@ -1,5 +1,5 @@
 project('gpioplus', 'cpp',
-        version: '0.1', meson_version: '>=0.49.0',
+        version: '0.1', meson_version: '>=0.53.2',
         default_options: [
           'warning_level=3',
           'werror=true',