Add build tracing

This creates a rotating build.trace.gz in the out directory that can be
loaded with chrome://tracing. It'll include start and end timings for
make/soong/kati/ninja, and it will import and time-correct the ninja log
files.

Test: m -j; load out/build.trace.gz in chrome://tracing
Test: multiproduct_kati -keep; load out/multiproduct*/build.trace.gz
Change-Id: Ic060fa9515eb88d95dbe16712479dae9dffcf626

ui/build/Android.bp

@@ -17,6 +17,7 @@ bootstrap_go_package {
     pkgPath: "android/soong/ui/build",
     deps: [
         "soong-ui-logger",
+        "soong-ui-tracer",
     ],
     srcs: [
         "build.go",