Work around broken ln on solaris as used in t8006

The test setup in t8006-blame-textconv.sh uses "ln -sf" to
overwrite an existing symlink.  Unfortunately, both /usr/bin/ln
and /usr/xpg4/bin/ln on solaris 9 don't properly handle -f and -s
used at the same time.  This caused the test setup and subsequent
checks to fail.

Instead, remove the symlink and then create a new one in the
setup code.

The upstream Solaris bug (fixed in 10, but not 9) is documented
here:

  http://bugs.opensolaris.org/view_bug.do?bug_id=4372462

Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t8006-blame-textconv.sh

@@ -25,7 +25,8 @@ test_expect_success 'setup ' '
 	echo "bin: test 1 version 2" >one.bin &&
 	echo "bin: test number 2 version 2" >>two.bin &&
 	if test_have_prereq SYMLINKS; then
-		ln -sf two.bin symlink.bin
+		rm symlink.bin &&
+		ln -s two.bin symlink.bin
 	fi &&
 	GIT_AUTHOR_NAME=Number2 git commit -a -m Second --date="2010-01-01 20:00:00"
 '