CTestCustom: Suppress warnings about rand() and srand() on OpenBSD

We don't do crypto here, so a "poor" random doesn't matter. In fact we have API
to allow people to get a repeatable sequence by setting a specific seed.

CTestCustom.cmake.in

@@ -55,6 +55,8 @@ set(CTEST_CUSTOM_WARNING_EXCEPTION
   "warning.*This version of Mac OS X is unsupported"
   "clang.*: warning: argument unused during compilation: .-g"
   "note: in expansion of macro" # diagnostic context note
+  "cm(StringCommand|CTestTestHandler)\\.cxx.*warning.*rand.*isn.*t random" # we do not do crypto
+  "cm(StringCommand|CTestTestHandler)\\.cxx.*warning.*srand.*seed choices are.*poor" # we do not do crypto
 
   # Ignore clang's summary warning, assuming prior text has matched some
   # other warning expression: