tcmode-external-sourcery: create ld.bfd toolchain symlink

Now that KERNEL_LD uses ld.bfd, we need to ensure that it exists when using an
external toolchain.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode-external-sourcery: don't break when not in a loop

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
layer.conf: also include recipes-*

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Split linux-libc-headers out of external-sourcery-toolchain

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
csl-versions.inc: grab binutils version

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode: change CSL_TARGET_SYS back to its original meaning

This retains the ability to specify multiple possible toolchain prefixes,
while having CSL_TARGET_SYS as the one which actually exists.

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