ocaml: make sure to pass LDFLAGS to ocamlmklibs linker (RHBZ#1624130)

Pass the LDFLAGS properly as arguments for the C linker when using
ocamlmklibs via the -ldopt option.

Followup of commit 34c23403c5.

(cherry picked from commit 4ff573c352)

ocaml/Makefile.am

@@ -64,14 +64,14 @@ endif
 
 stamp-mlguestfs: libguestfsocaml.a $(guestfs_cmm)
 	$(OCAMLMKLIB) -o mlguestfs \
+	  -ldopt '$(LDFLAGS)' \
 	  $(libguestfsocaml_a_OBJECTS) guestfs.cmo \
-	  $(LDFLAGS) \
 	  $(LTLIBINTL) \
 	  -L../lib/.libs -lguestfs
 if HAVE_OCAMLOPT
 	$(OCAMLMKLIB) -o mlguestfs \
+	  -ldopt '$(LDFLAGS)' \
 	  $(libguestfsocaml_a_OBJECTS) guestfs.cmx \
-	  $(LDFLAGS) \
 	  $(LTLIBINTL) \
 	  -L../lib/.libs -lguestfs
 endif