Commit 6c213e863a ("http-backend: respect CONTENT_LENGTH for
receive-pack", 2018-07-27) adds a test which uses the non-portable
export construct. Replace it with "FOO=bar && export FOO" instead.
Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>