https://github.com/ClusterLabs/libqb/pull/440
https://bugs.gentoo.org/775605

From 84c09815fee4d1c2571ed1ef772812cac470a8f3 Mon Sep 17 00:00:00 2001
From: orbea <orbea@riseup.net>
Date: Tue, 16 Mar 2021 11:13:45 -0700
Subject: [PATCH] build: Fix undefined pthread reference.
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -38,7 +38,8 @@ bmc_SOURCES = bmc.c
 bmc_LDADD = $(top_builddir)/lib/libqb.la
 
 bmcpt_SOURCES = bmcpt.c
-bmcpt_LDADD = $(top_builddir)/lib/libqb.la
+bmcpt_CFLAGS = $(PTHREAD_CFLAGS)
+bmcpt_LDADD = $(PTHREAD_LIBS) $(top_builddir)/lib/libqb.la
 
 bms_SOURCES = bms.c
 bms_CFLAGS = $(GLIB_CFLAGS)