.gitattributes: ensure t/oid-info/* has eol=lf

The new test_oid machinery in the test library requires reading
some information from t/oid-info/hash-info and t/oid-info/oid.

The logic to read from these files in shell uses built-in "read"
command, which leaves CR at the end of these text files when they
are checked out with CRLF line endings, at least when run with bash
shipped with Git for Windows.  This results in an unexpected value
in the variable these lines are read into, leading the tests to
fail.

Mark them to be checked out always with the LF line endings.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitattributes

@@ -9,3 +9,4 @@
 /command-list.txt eol=lf
 /GIT-VERSION-GEN eol=lf
 /mergetools/* eol=lf
+/t/oid-info/* eol=lf