Remove gtest

It would be useful to be able to run libcper decoding unit tests without
needing a C compiler, as would be required if this were compiled to a
python module.

Change-Id: I183bc9ef048c336205186ea449e15b7766b19990
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/subprojects/packagefiles/jsoncdac/meson.build b/subprojects/packagefiles/jsoncdac/meson.build
index 6cc3bfc..f7af58f 100644
--- a/subprojects/packagefiles/jsoncdac/meson.build
+++ b/subprojects/packagefiles/jsoncdac/meson.build
@@ -2,7 +2,7 @@
     'libjsoncdac',
     ['c'],
     meson_version: '>=1.1.1',
-    default_options: ['default_library=static', 'c_std=gnu23'],
+    default_options: ['default_library=static', 'c_std=gnu18'],
 )
 conf_data = configuration_data(
     {