pkg/52125: pkg_create does not use multiple threads

[n54%gmx.com@localhost]

>Number:         52125
>Category:       pkg
>Synopsis:       pkg_create does not use multiple threads
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 30 21:35:00 +0000 2017
>Originator:     Kamil Rytarowski
>Release:        NetBSD 7.99.66 amd64
>Organization:
TNF
>Environment:
NetBSD chieftec 7.99.66 NetBSD 7.99.66 (GENERIC) #6: Wed Mar 29 21:21:19 CEST 2017  root@chieftec:/public/netbsd-root/sys/arch/amd64/compile/GENERIC amd64
>Description:
Example CPU usage during package creation:

CPU0 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU1 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU2 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU3 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU4 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU5 states:  1.4% user,  0.0% nice,  0.0% system,  0.0% interrupt, 98.6% idle
CPU6 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU7 states: 95.9% user,  0.0% nice,  4.1% system,  0.0% interrupt,  0.0% idle

Please try to reuse over multiple CPUs.

Creating very large packages takes very long - even in tmpfs.
>How-To-Repeat:
Try to build large package like llvm with debug info.
>Fix:
N/A