To monitor ninja inputs, generate ninja_inputs.pb as build metrics.
This will count the number of input files and required git projects,
with the number of files for each project.
Bug: 241033491
Test: $ cp .repo/manifests/default.xml out/dist/manifest_1.xml
$ development/multitree/build_vendor.sh -d vsoc_x86_64 \
-p cf_x86_64_phone -r out/dist -i 1
Change-Id: Ie185863f1c8fca313baba6135374d509e2d93937
With this change the exclude list file may have comments that start
with '#'
Test: Run collect_ninja_inputs.py with excluded file list that has
'#' comments
Change-Id: Ic2e3da8a34144426e00ebd45ee09ff9cb3b339bd
