golang `flag` package's default FlagSet `flag.CommandLine` calls
`flag.Usage` and `os.Exit(2)` on error to print the usage string.
Set `flag.Usage` to our custom usage function.
Test: m bpmodify; bpmodify -h; bpmodify --help
Change-Id: Ida107b0dbb07c291c3d7ea90eda9147d04a7cd51
Blueprint is a meta-build system that reads in Blueprints files that describe
modules that need to be built, and produces a
Ninja manifest describing the commands that
need to be run and their dependencies. Where most build systems use built-in
rules or a domain-specific language to describe the logic for converting module
descriptions to build rules, Blueprint delegates this to per-project build
logic written in Go. For large, heterogenous projects this allows the inherent
complexity of the build logic to be maintained in a high-level language, while
still allowing simple changes to individual modules by modifying easy to
understand Blueprints files.
3edfbc214a
