NINJA_STATUS format to show time spent per edge

[kaidokert]

NINJA_STATUS has %o to show overall finished rate of edges/per second, %c to show current edges/second, and %e elapsed time in seconds.

These are all helpful to diagnose slow builds, however, in some instances it would be really handy to see actual seconds taken per command. For example, custom non-compiler actions that run complex workflows, very slow linker execution on certain platforms and so on. Would a %q or something be reasonable to show this ?