build_image: remove eclean support

eclean will be done as a part of build_packages. Hence remove the
support for eclean in build_image.

BUG=b:230016693
TEST=CQ

Cq-Depend: chromium:3735647
Change-Id: I6c2905fedb34c600bbd26c76bcec4f246c25b807
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3735907
Reviewed-by: Cindy Lin <xcl@google.com>
Commit-Queue: Ram Chandrasekar <rchandrasekar@google.com>
Tested-by: Ram Chandrasekar <rchandrasekar@google.com>
Auto-Submit: Ram Chandrasekar <rchandrasekar@google.com>
1 file changed