Test repeated invocations of getrandom()

A single program that invokes getrandom() repeatedly should end up
with the same stream of bytes, regardless of how it chunks up the
reading from the entropy source.

This test already passses.  I'm including it because it seems
like a useful confirmation.

.gitignore

@@ -6,6 +6,7 @@ test/lib*.o
 test/lib*.so
 test/use_lib_random
 test/use_lib_getpid
+test/repeat_random
 
 src/libfaketime.dylib.1
 src/libfaketime.1.dylib