Mark test "error message from query_search_messages" (T060-count.sh) to require GDB

[Milton Vandersloot]

Dear notmuch Developers

The test "error message from query_search_messages" in test/T060-count.sh needs GDB as external dependency but does not advocate so.
Below a sed script adding the requirement.

I have used ${TEST_GDB} here as this is the expression used in test/test-lib.sh at the end.
However, the test code base also has occurrences of "test_require_external_prereq gdb" (use grep or similar to find those).
I don't know which is the correct form but they should probably be unified.

Regards
Milton

# Mark tests properly which need GDB
sed -e "/test_begin_subtest [\"']error message from query_search_messages[\"']/ a test_require_external_prereq \\\${TEST_GDB}" \
	-i test/T060-count.sh || die