Add some profiling instrumentation

A few projects take a very long time between the log is opened and the build is actually started, mainly Android projects:

(datetime.timedelta(seconds=40), 'fonts-macos-x86_64.log')
(datetime.timedelta(seconds=40), 'fonts-windows-i686.log')
(datetime.timedelta(seconds=42), 'fonts-linux-x86_64.log')
(datetime.timedelta(seconds=42), 'fonts-windows-x86_64.log')
(datetime.timedelta(seconds=49), 'llvm-runtimes-android-armv7.log')
(datetime.timedelta(seconds=104), 'tor-android-service-android-armv7.log')
(datetime.timedelta(seconds=125), 'tor-onion-proxy-library-android-armv7.log')
(datetime.timedelta(seconds=189), 'application-services-android-armv7.log')
(datetime.timedelta(seconds=223), 'geckoview-android-armv7.log')
(datetime.timedelta(seconds=228), 'geckoview-android-x86.log')
(datetime.timedelta(seconds=228), 'geckoview-android-x86_64.log')
(datetime.timedelta(seconds=232), 'geckoview-android-aarch64.log')
(datetime.timedelta(seconds=387), 'android-components-android-x86_64.log')
(datetime.timedelta(seconds=399), 'android-components-android-aarch64.log')
(datetime.timedelta(seconds=405), 'android-components-android-armv7.log')
(datetime.timedelta(seconds=406), 'android-components-android-x86.log')
(datetime.timedelta(seconds=430), 'fenix-android-x86_64.log')
(datetime.timedelta(seconds=443), 'fenix-android-aarch64.log')
(datetime.timedelta(seconds=447), 'fenix-android-x86.log')
(datetime.timedelta(seconds=456), 'fenix-android-armv7.log')
(datetime.timedelta(seconds=461), 'firefox-android-android-armv7.log')

AC and Fenix isn't a big deal, since we're switching to firefox-android only very soon.

However, it would be great to get a way of profiling why these projects are taking so long.

I think an option to print what's happening would work, too, at least to understand the problems.