With these changes it will be easier to maintain, i.e. to add/remove bottles
just modify the `BOTTLES :=` list.
`brew update` is removed from `scripts/fetch-brew-bottle.sh` and instead done
in an [order-only
prerequisite](https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html). This
allows multiple bottles to be fetched in parallel (e.g. `make -j16`) without
overlapping invocations of `brew update` (which causes script failure).
It's not supported to run `brew update` multiple times simultaenously. A better
fix for this can be implemented, but for now in the Makefile have target
`bottles/pcre` depend on target `bottles/openssl` so that they run serially
when `-jN` is passed to `make`.
I was originally going to change `brew update >/dev/null` to
`brew update >/dev/null || true` but decided the Makefile change provides a
better guarantee that simultaenous `brew` commands won't interfere with each
other. In the process, I revised some of the script's `echo` output just a bit.
Michael Bradley, Jr