[roll_boringssl] Return to separate repositories

16e9935 reorganized this repository to contain the upstream repository,
but forgot to remove `src/` from `.gitignore`.

Rather than check in the entire upstream repository (losing its git
history in the process), make the minimum change to return to the old
state so that boringssl can be updated in the short term.

```
go run roll_boringssl.go \
  --commit f9c8d30897c0acdb8ba8358ae8c0970a65bd7e2d
```

```
git mv README.fuchsia{.md,}
```

16e9935 made the opposite change but the documentation specifies the
name `README.fuchsia`:

https://fuchsia.googlesource.com/fuchsia/+/7834818/docs/concepts/source_code/third-party-metadata.md

Refactor roll_boringssl.go to improve error checking, remove globals,
and clean up unnecessary newlines (the log package always appends a
newline).

Change-Id: I0ca91d76f64fec2ca92c3f8d991e74b0e06c1d5f
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/boringssl/+/376395
Reviewed-by: Craig Tiller <ctiller@google.com>
Commit-Queue: Tamir Duberstein <tamird@google.com>
3 files changed