t9001: PATH must not use Windows-style paths

On Windows, $(pwd) returns a drive-letter style path C:/foo, while $PWD
contains a POSIX style /c/foo path. When we want to interpolate the
current directory in the PATH variable, we must not use the C:/foo style,
because the meaning of the colon is ambiguous. Use the POSIX style.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9001-send-email.sh

@@ -2099,7 +2099,7 @@ test_expect_success $PREREQ 'leading and trailing whitespaces are removed' '
 
 test_expect_success $PREREQ 'test using command name with --sendmail-cmd' '
 	clean_fake_sendmail &&
-	PATH="$(pwd):$PATH" \
+	PATH="$PWD:$PATH" \
 	git send-email \
 		--from="Example <nobody@example.com>" \
 		--to=nobody@example.com \