test/signal: Convert to googletest

Catch2 never really took off and googletest mostly gives us everything
we need.

Change-Id: Ib11edb94470c3b66c3acb2196de52fa03d311923
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/meson.build b/test/meson.build
index 4ffd1a9..8e17d71 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -3,6 +3,7 @@
   'exception',
   'handle/copyable',
   'handle/managed',
+  'signal',
   'util/cexec',
   'util/string',
 ]
@@ -137,7 +138,6 @@
 endif
 
 catch2_tests = [
-  'signal',
   'raw',
 ]