A few cleanups in Makefile.am

A lot of the lists in Makefile.am were not sorted properly (or at
all); let's sort them for more sanity.

Additionally, check-local used to spew this big shell block, even
though it does emit nice messages when failing, so we don't need to
show the code; let's silence it (@).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>