binman: Support building a selection of images

Sometimes it is useful to build only a subset of the images provided by
the binman configuration. Add a -i option for this. It can be given
multiple times to build several images. If the option is not given, all
images are built.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/cmdline.py b/tools/binman/cmdline.py
index f0de4de..4ce8bc6 100644
--- a/tools/binman/cmdline.py
+++ b/tools/binman/cmdline.py
@@ -30,6 +30,8 @@
             help='Enabling debugging (provides a full traceback on error)')
     parser.add_option('-E', '--entry-docs', action='store_true',
             help='Write out entry documentation (see README.entries)')
+    parser.add_option('-i', '--image', type='string', action='append',
+            help='Image filename to build (if not specified, build all)')
     parser.add_option('-I', '--indir', action='append',
             help='Add a path to a directory to use for input files')
     parser.add_option('-H', '--full-help', action='store_true',