Show elapsed time in minutes if >= 60 secs
In large projects with long compile times, seeing "428.65 secs" isn't as clear to humans as seeing the number of minutes (and seconds).
**Old**:
```
Finished dev [unoptimized + debuginfo] target(s) in 2.23 secs
Finished dev [unoptimized + debuginfo] target(s) in 63.94 secs
Finished dev [unoptimized + debuginfo] target(s) in 428.65 secs
```
**New**:
```
Finished dev [unoptimized + debuginfo] target(s) in 2.23s
Finished dev [unoptimized + debuginfo] target(s) in 1m 3.94s
Finished dev [unoptimized + debuginfo] target(s) in 7m 8.65s
```
Note that I also changed `secs` to `s`, because `7 mins 8.65 secs` and `7m 8.65 secs` both look strange IMO. But if you disagree and you'd prefer `secs`, just tell me and I'll change it.
I *didn't* add a check for `secs >= 3600` to print the time in hours. I *hope* this is not necessary...
420f9ec576