layer.conf: add layer specific areas

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
README.md: resurrect rebuild-libc bits

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
external-sourcery-toolchain: Error out if libc.so does not exist

Depending on the external toolchain config, the libc.so file may
not exist.   This generally means that the machine config does
not have multi-lib support when it should.  Rather than letting
the "sed" command error out with a cryptic message, issue a
(hopefully) more meaningful message.

Signed-off-by: Drew Moseley <drew_moseley@mentor.com>
Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode-external-sourcery: Add x86_64-amd-linux-gnu toolchain prefix.

Allow x86-64 builds to use x86_64-amd-linux-gnu as the prefix for the
cross tools.

Signed-off-by: Drew Moseley <drew_moseley@mentor.com>
Signed-off-by: Christopher Larson <chris_larson@mentor.com>
(cherry picked from commit 45d049fa9176a8e21f3132561add246f9ad8970f)
external-sourcery-toolchain: add the Transactional Memory library

Signed-off-by: Drew Moseley <drew_moseley@mentor.com>
Signed-off-by: Christopher Larson <chris_larson@mentor.com>
(cherry picked from commit d6a4bae507fa24139d36150b9d5ef5bc6e74ad65)
Pull over current master bbappends

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Update TODO

Signed-off-by: Christopher Larson <chris_larson@mentor.com>