[FR]: control `minify` behavior with a flag

[alexeagle]

What is the current behavior?

Developers need to minify for production, but minified code during development is just a nuisance. This is a common pattern in compilers which can produce "stripped" or "optimized" vs. "debug" binaries.

Currently the minify flag has to be a boolean in the BUILD file, so developers have to manually change it, or use a select to make it configurable based on some command-line flag.

Describe the feature

We should probably just honor the --compilation_mode flag, as many Bazel users have --compilation_mode=opt in their release configuration. For backwards compat, we could have trinary similar to stamping behavior:

• minify = True is always minify
• minify = False is never minify
• minify = None is "honor the --compilation_mode"