Filter kati output to collapse verbose messages

1. Collapses the "including .../Android.mk ..." lines like ninja does,
so that we overwrite the last line if there wasn't anything else to
print.
2. Strips ansi control codes so that log files don't include unreadable
characters.

Test: m -j
Test: m -j | tee output.log   (with colored output)
Change-Id: Ib18437f6f9d37084360097a9d586800c833072c5

ui/build/context.go

@@ -95,3 +95,10 @@ func (c ContextImpl) ImportNinjaLog(filename string, startOffset time.Time) {
 		c.Tracer.ImportNinjaLog(c.Thread, filename, startOffset)
 	}
 }
+
+func (c ContextImpl) IsTerminal() bool {
+	if term, ok := os.LookupEnv("TERM"); ok {
+		return term != "dumb" && isTerminal(c.Stdout()) && isTerminal(c.Stderr())
+	}
+	return false
+}