tools/ocaml: Specify rpath correctly for ocamlmklib

ocamlmklib has special handling for C-like '-Wl,-rpath' option, but does
not know how to handle '-Wl,-rpath-link', as evidenced by warnings like:
"Unknown option
-Wl,-rpath-link=$HOME/xen/tools/ocaml/libs/eventchn/../../../../tools/libs/toollog"
Pass this option directly to the compiler with -ccopt instead.

Also pass -L directly to the linker with -ldopt. This prevents embedding absolute
paths from buildtime into binary's RPATH.

Fixes: f7b4e4558b ("tools/ocaml: Fix OCaml libs rules")
Reported-by: Fernando Rodrigues <alpha@sigmasquadron.net>
Tested-by: Fernando Rodrigues <alpha@sigmasquadron.net>
Signed-off-by: Andrii Sultanov <andrii.sultanov@cloud.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>

tools/ocaml/Makefile.rules

@@ -63,7 +63,7 @@ mk-caml-lib-bytecode = $(call quiet-command, $(OCAMLC) $(OCAMLCFLAGS) -a -o $1 $
 
 mk-caml-stubs = $(call quiet-command, $(OCAMLMKLIB) -o `basename $1 .a` $2,MKLIB,$1)
 mk-caml-lib-stubs = \
-	$(call quiet-command, $(OCAMLMKLIB) -o `basename $1 .a | sed -e 's/^lib//'` $2 $3,MKLIB,$1)
+	$(call quiet-command, $(OCAMLMKLIB) -o `basename $1 .a | sed -e 's/^lib//'` $2 `echo $3 | sed -e 's/-ccopt -l/-l/g' | sed -e 's/-ccopt -L/-ldopt -L/g'`,MKLIB,$1)
 
 # define a library target <name>.cmxa and <name>.cma
 define OCAML_LIBRARY_template
@@ -74,7 +74,7 @@ define OCAML_LIBRARY_template
  $(1)_stubs.a: $(foreach obj,$$($(1)_C_OBJS),$(obj).o)
 	$(call mk-caml-stubs,$$@, $$+)
  lib$(1)_stubs.a: $(foreach obj,$($(1)_C_OBJS),$(obj).o)
-	$(call mk-caml-lib-stubs,$$@, $$+, $(foreach lib,$(LIBS_$(1)),$(lib)))
+	$(call mk-caml-lib-stubs,$$@, $$+, $(foreach lib,$(LIBS_$(1)),-ccopt $(lib)))
 endef
 
 # Dynamically linked OCaml libraries ("plugins" in Dynlink parlance)