Fix tests-printers handling for cross compiling.

The pretty-printers changes resulted in the new tests showing as
UNRESOLVED (missing .out files) when run-built-tests = no, so
resulting in "make check" exiting with error status.

https://sourceware.org/ml/libc-testresults/2016-q4/msg00014.html

This patch moves the use of $(tests-printers) when generating the
summary of results into the setting of tests-expected, which is
appropriately conditional, matching the conditional for when tests
depends on $(tests-printers-out).

Tested with cross to aarch64 with build-many-glibcs.py, and natively
on x86_64.

	* Rules [$(run-built-tests) != no] (tests-expected): Add
	$(tests-printers).
	(tests): Do not pass $(tests-printers) to merge-test-results.sh.