Do not warn in check-config script about ext3 if provided by ext4

Many distributions now use ext4 to provide ext2 and ext3 support,
so do not warn about possibly missing ext3 support if the config
option is used.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

contrib/check-config.sh

@@ -238,14 +238,20 @@ flags=(
 )
 check_flags "${flags[@]}"
 
-check_flags EXT3_FS EXT3_FS_XATTR EXT3_FS_POSIX_ACL EXT3_FS_SECURITY
-if ! is_set EXT3_FS || ! is_set EXT3_FS_XATTR || ! is_set EXT3_FS_POSIX_ACL || ! is_set EXT3_FS_SECURITY; then
-	echo "    $(wrap_color '(enable these ext3 configs if you are using ext3 as backing filesystem)' bold black)"
+if ! is_set EXT4_USE_FOR_EXT2; then
+	check_flags EXT3_FS EXT3_FS_XATTR EXT3_FS_POSIX_ACL EXT3_FS_SECURITY
+	if ! is_set EXT3_FS || ! is_set EXT3_FS_XATTR || ! is_set EXT3_FS_POSIX_ACL || ! is_set EXT3_FS_SECURITY; then
+		echo "    $(wrap_color '(enable these ext3 configs if you are using ext3 as backing filesystem)' bold black)"
+	fi
 fi
 
 check_flags EXT4_FS EXT4_FS_POSIX_ACL EXT4_FS_SECURITY
 if ! is_set EXT4_FS || ! is_set EXT4_FS_POSIX_ACL || ! is_set EXT4_FS_SECURITY; then
-	echo "    $(wrap_color 'enable these ext4 configs if you are using ext4 as backing filesystem' bold black)"
+	if is_set EXT4_USE_FOR_EXT2; then
+		echo "    $(wrap_color 'enable these ext4 configs if you are using ext3 or ext4 as backing filesystem' bold black)"
+	else
+		echo "    $(wrap_color 'enable these ext4 configs if you are using ext4 as backing filesystem' bold black)"
+	fi
 fi
 
 echo '- Network Drivers:'