t3032-*.sh: Do not strip CR from line-endings while grepping on MinGW

t3032-*.sh: Do not strip CR from line-endings while grepping on MinGW

By default grep reads in text mode and converts CRLF into LF line
endings, which causes tests 4, 6 and 8 to fail. In a similar manner
to commit a94114ad  (Do not strip CR when grepping HTTP headers,
2010-09-12), we set (and export) the GREP_OPTIONS variable to -U so
that grep will use binary mode.

Signed-off-by: Ramsay Jones <redacted>
Acked-by: Johannes Sixt <redacted>
Signed-off-by: Junio C Hamano <redacted>