all.sh restores **/Makefile from git in case the version in the worktree was
from doing a cmake in-tree build. Instead of doing this unconditionally, do
it only if the toplevel Makefile seems to have been automatically
generated (by cmake or otherwise, e.g. by mbedtls-prepare-build). This way
all.sh no longer silently wipes changes made to Makefile but not committed yet.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>