http://bugs.gentoo.org/514008

--- dc1394/usb/Makefile.am
+++ dc1394/usb/Makefile.am
@@ -8,7 +8,7 @@
 endif
 
 AM_CFLAGS = -I$(top_srcdir) -I$(top_srcdir)/dc1394 $(LIBUSB_CFLAGS)
-libdc1394_usb_la_LIBADD = $(LIBUSB_LIBS)
+libdc1394_usb_la_LIBADD = $(LIBUSB_LIBS) -lpthread
 libdc1394_usb_la_SOURCES =  \
 	control.c \
 	usb.h \