Hack around wall clock time going backwards.

As reported in https://github.com/jmmv/kyua/issues/155, the wall clock
time can go backwards resulting in an apparent negative delta. As
a workaround, convert such deltas to 1us. This allows tests to run
successfully in MIPS64 qemu.

Approved by:	jmmv (maintainer)
Sponsored by:	DARPA, AFRL

devel/kyua/Makefile

@@ -3,6 +3,7 @@
 PORTNAME=	kyua
 PORTVERSION=	0.13
 PORTEPOCH=	3
+PORTREVISION=	1
 CATEGORIES=	devel
 MASTER_SITES=	https://github.com/jmmv/kyua/releases/download/${PORTNAME}-${PORTVERSION}/ \
 		LOCAL/jmmv

devel/kyua/files/patch-utils_datetime.cpp

@@ -0,0 +1,23 @@
+
+$FreeBSD$
+
+--- utils/datetime.cpp.orig
++++ utils/datetime.cpp
+@@ -590,11 +590,12 @@
+ datetime::delta
+ datetime::timestamp::operator-(const datetime::timestamp& other) const
+ {
+-    if ((*this) < other) {
+-        throw std::runtime_error(
+-            F("Cannot subtract %s from %s as it would result in a negative "
+-              "datetime::delta, which are not supported") % other % (*this));
+-    }
++    /*
++     * XXX-BD: gettimeofday isn't necessicarily monotonic so return the
++     * smallest non-zero delta if time went backwards.
++     */
++    if ((*this) < other)
++        return datetime::delta::from_microseconds(1);
+     return datetime::delta::from_microseconds(to_microseconds() -
+                                               other.to_microseconds());
+ }