build: ensure silent Make behavior for json scripts

build: ensure silent Make behavior for json scripts

Run the invocation of Make with verbosity in order to
prevent the printing of Makefile level and subtarget status.
e.g.  make[3] -C target/linux val.DEFAULT_PACKAGES val.ARCH_PACKAGES

Remove piping of stderr, which is only useful when using
the "communicate" method over the "run" method,
and this script would not be written to handle a captured error anyway.

For error testing, stdout and stderr can be set to a file object
with the open() function like this:

out = open('json_out', 'w')
err = open('json_err', 'w')

...
...
stdout=out,
stderr=err,

Signed-off-by: Michael Pratt <mcpratt@pm.me>