dibbler: Add libpthread to linker flags

Fixed build issue
lowlevel-linux-link-state.c:(.text+0x450): undefined reference to `pthread_create'
clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-connectivity/dibbler/dibbler_git.bb

@@ -29,6 +29,8 @@ inherit autotools
 
 DEPENDS += "flex-native"
 
+LDFLAGS += "-pthread"
+
 PACKAGES =+ "${PN}-requestor ${PN}-client ${PN}-relay ${PN}-server"
 
 FILES_${PN}-client = "${sbindir}/${PN}-client"