Use case

As a developer targeting embedded devices, I wish to build the flutter engine optimized for size rather than speed as it is advantageous on some platforms to reduce the binary footprint as much as possible.

Proposal

Add a flag to the engine/src/flutter/tools/gn tool to enable size optimizations, eg

/engine/src/flutter/tools/gn --optimize-for-size

The flags --optimize-for-size and --unoptimized should probably be mutually exclusive