Feature Request: Support optimization flags in the build actions

[sanathkr]

Description:
We can support several optimizations to improve the build process. This is a feature request to support optimization flags that can be passed to each build action. If an action cannot support a particular optimization, it should error out:

Optimization 1: Use prebuilt binaries

Benefit: Makes build faster

When building dependencies with native modules, use pre-built binaries that are available locally or download from internet. This saves time in recompiling the same binaries over and over again. It can also make the build more stable because sometimes compilation fails or times out.

Requested by build actions:

1. node-npm
2. python-pip

Optimization 2: Remove unnecessary dependencies

Benefit: Produces slim zips

Remove unnecessary dependency libraries, or files or folders from the output artifact. For example, remove tests, test data files, or dependencies that are already available in transitive closure.

Requested by build actions:

1. node-npm
2. python-pip

[gojko]

A combination of PRs (#63 and #53) removes the need for this in Node. People can configure packaging sufficiently with this so that further flags aren't really needed. If you decide to implement something globally later for other builders, we could use the same flags to automate these steps further.

[abrooksv]

Why should it error out instead of no-op'ing with a note about unsupported swtich? If sam build is the abstraction over all the build systems, it should strive to achieve a common API for the callers to know, and not leak the implementation details of what builders support what switches.