Makefile: Update symlink target

This almost completely replaces the original symlink target for creating
symbolic links from site-local into the coreboot tree. Changes include:

- A comment about the format of the symlink.txt file
- Verify that there are symlink.txt files before doing anything.
- Note that symbolic links that already exist are being skipped.
- Only use the first line of the symlink.txt file
- Make sure the symbolic link to be created is inside the coreboot dir.
- Output errors to STDERR
- echo -e isn't supported by posix shells, so replace /t with two spaces

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: I9b0d1b5bc19556bc41ca98519390e69ea104bd1b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83122
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Eric Lai <ericllai@google.com>

0 files changed, 0 insertions, 0 deletions