toolchain/58221: make can't handle libntp Makefile

[campbell+netbsd%mumble.net@localhost]

>Number:         58221
>Category:       toolchain
>Synopsis:       make can't handle libntp Makefile
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 02 20:50:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The ${%NetBSD:L${:Ufoundation}}
>Environment:
>Description:
Using a newly-built nbmake from trunk as of today:

$ pwd
/home/riastradh/netbsd/git/src/external/bsd/ntp/lib/libntp
$ ~/netbsd/current/obj.sparc64/tooldir/bin/nbmake MKREPRO=yes -v CPPFLAGS.ntp_calendar.c                      
nbmake: "/home/riastradh/netbsd/git/src/external/bsd/ntp/lib/libntp/Makefile" line 90: while evaluating variable "%b %e %Y": Invalid time value ""
nbmake: "/home/riastradh/netbsd/git/src/external/bsd/ntp/lib/libntp/Makefile" line 90: Undefined variable "${%b %e %Y:L:${:Ugmtime=${MKREPRO_TIMESTAMP}}:"
nbmake: "/home/riastradh/netbsd/git/src/external/bsd/ntp/lib/libntp/Makefile" li
ne 90: while evaluating variable "%T": Invalid time value ""                    nbmake: Fatal errors encountered -- cannot continue
nbmake: stopped in /home/riastradh/netbsd/git/src/external/bsd/ntp/lib/libntp

>How-To-Repeat:
run nbmake in external/bsd/ntp/lib/libntp
>Fix:
Yes, please!