Don't build size reports without bloaty configured
Don't build size reports without bloaty configured

This change updates the pw_size_report template to emit an empty group
if the bloaty config build arg is not set, to prevent projects from
having to configure bloaty when depending on a module that includes size
reports.

Change-Id: Ia80dd5c9398bba6fb274fa92ec343a5226169427

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed