Replaced ci.bazelrc and v8-ci.bazelrc by custom configs inside the main
.bazelrc file. As a result, github workflows setup is simplified down to
a single '--config=<foo>' flag usage.
Moved the build metadata flags to config=ci.
Added custom tags metadata to help differentiate invocations based on
workflow (bazel vs v8) and os (linux/macos/windows).
Enabled users to override the default values in .bazelrc by using a
user.bazelrc file locally.
Added user.bazelrc to gitignore.
Alternative approach, we use rusty_v8 for all platforms that its
predefined, but lets build from source a musl v8 version with bazel for
x86 and aarch64 only. We would need to release this on github and then
use the release.
