Build with kati+ninja when USE_NINJA=true

Build with kati+ninja when USE_NINJA=true

If USE_NINJA=true, use kati to translate makefiles into ninja files,
and then execute them with ninja.

Builds kati from source using simplified versions of the rules
in binary.mk and definitions.mk.

Adds two new goals when USE_NINJA=true: generateonly will regenerate
build.ninja but not rebuild (useful for comparing build.ninja output
between runs), and fastincremental will skip regenerating build.ninja
and go directly to running ninja, providing ~5 second incremental
builds.

Change-Id: Ib85399e730f1fbb1be7371fafeee7d1c31080771