build: use allowed over enabled

Meson feature options are typically in a tri-state of enabled, disabled,
or auto.  The enabled and disabled functions on an option (from
`get_option`) no longer return true for auto features.  Instead, the
expectation is to use `allowed()` which is true for both enabled and auto.

Switch all uses of `enabled` to `allowed`.

Change-Id: I91fe34f9d6743a3afeef73c3e55847542cea143c
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/subprojects/ncsid/test/meson.build b/subprojects/ncsid/test/meson.build
index 27c2f8b..681306f 100644
--- a/subprojects/ncsid/test/meson.build
+++ b/subprojects/ncsid/test/meson.build
@@ -30,7 +30,7 @@
       ])
     gmock = gtest_proj.dependency('gmock')
   else
-    assert(not build_tests.enabled(), 'Googletest is required')
+    assert(not build_tests.allowed(), 'Googletest is required')
   endif
 endif