Store the value from TARGET_OTA_ASSERT_DEVICE to a file

This is needed so it can be read in when re-signing a package to
allow for the proper device asserts.

Change-Id: I8f3bb491bbbaa4d2b827a45ef83f12c6c83e6712
build: Add time taken to Brunch/Make carbon builds

This allows the displaying of time taken between builds by default.
It's pretty much a shortcut instead of typing time in front of it.

Change-Id: I9926c954adbcb9b1e2a783000e738feec7f3c9dd
Merge remote-tracking branch 'upstream/kk' into fjcarbon