Entry point for the flixw compiler-metrics plugin.

Two phases in two JVMs, and the split is forced rather than chosen. The compiler resolves the Java classes its own standard library imports through the application class path, so flix.jar has to be flat on -cp -- see ReflectionEngine#measure. This process cannot put it there after the fact, so it re-launches itself with --bridge.

The 270ms that costs is why the cache is consulted here, in the outer phase: a hit answers without the second JVM and without the compiler, in about a tenth of a second against roughly four seconds.