ON-16450: Fix ZF_DEVEL=1 builds

Fix the following build-time error:

  $ ZF_DEVEL=1 ONLOAD_TREE=... make
  ...
  /usr/bin/ld: cannot find -lciul1
  collect2: error: ld returned 1 exit status

A problem here was src/tests/zf_unit/Makefile.inc setting LD_FLAGS
and these being passed to src/tests/trade_sim/Makefile indirectly
via the top-level Makefile. It is only a problem when Onload is
not installed in the OS.

Author: ivatet-amd

src/tests/zf_unit/Makefile.inc

@@ -85,8 +85,6 @@ $(UT_BINS): $(UT_BINDIR)/%: $(OBJ_CURRENT)/%.o
 $(UT_BINS): $(OBJ_CURRENT)/../tap/tap.o
 $(UT_BINS): $(ZF_STATIC_LIB) $(CIUL_LIB)
 
-LDFLAGS += -lciul1
-
 $(UT_BINS):
 	@mkdir -p $(dir $@)
 	$(CLINK) $^ -lm -lpthread -lrt -ldl -lstdc++ -o $@