Having separate .ninja_log files doesn't work very well after
04d886b110
since the last successful timestamp is not recorded in the ninja log.
This was triggering the primary builder to be run twice on every build
since it was always considered out of date in the primary, then main
stages.
The two bootstrap stages already were unified when minibootstrap was
simplified, but this combines the main stage as well. This means that
we'll save some time running globs that are shared between minibp and
the primary builder as well (subdirs globs).
The cleanup code needed to be refactored, since the ninja_log will have
entries from the main stage as well. So instead of looking at everything
in the ninja log, take a string prefix to limit what we may clean.
Change-Id: I8d43168643aa8a0c6c3e48c6101eaa45d174bbe5
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.