This should be reassigned to xfce4-dev-tools once there's a bugzilla component for it. -Wl,--as-needed (ie linker opts) shouldn't be added when --enable-debug=full is used, as on OpenBSD things get messed up when --as-needed is used in conjunction with -pthread. See http://buildbot.xfce.org/builders/libxfce4util-openbsd/builds/14/steps/gmake%20distcheck/logs/stdio Ideally, m4macros/xdt-features.m4 should do the AC_MSG_CHECKING([whether $LD accepts --as-needed]) only if uname is != OpenBSD, as done for adding -Wredundant-decls. Or conditionally add -Wl,--as-needed to LDFLAGS just below.
Created attachment 3643 don't check for --as-needed on OpenBSD Quite intrusive one
Created attachment 3644 Don't add --as-needed to LDFLAGS on OpenBSD smaller one
Applied in 874bfb8.
I'm not reopening this but it seems like OpenBSD's pkg-config is packaged wrongly if this happens. It should be ./configured with --enable-indirect-deps to inherit -pthread where needed (that's what Gentoo's pkg-config is doing for FreeBSD).
We don't use fd.o's pkg-config, but our own written in perl (which is 10x smaller, and doesn't depend on glib, etc..) - and it doesn't have support for 'indirect deps', whatever that is.