Correctly copy the board configuration input variables

dict(**h[0]) was only copying the top level dictionary
object, but not any other dictionaries/lists inside of
it. This was causing us to not find all the changes to
variables the board configuration was making, and so
some variables were not included in the output.

Bug: 201700692
Test: ./build/bazel/ci/rbc_regression_test.sh mainline_system_x86_64-userdebug
Test: ./out/soong/rbcrun ./build/make/tests/run.rbc
Change-Id: I4467eead7e597f6f49119a8c4832126f39d646e7