tools: Introduce $(xenlibs-ldflags, ) macro

This avoid the need to open-coding the list of flags needed to link
with an in-tree Xen library when using -lxen*.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>

tools/Rules.mk

@@ -105,6 +105,14 @@ define xenlibs-ldlibs
     $(foreach lib,$(1),$(xenlibs-ldlibs-$(lib)))
 endef
 
+# Provide needed flags for linking an in-tree Xen library by an external
+# project (or when it is necessary to link with "-lxen$(1)" instead of using
+# the full path to the library).
+define xenlibs-ldflags
+    $(call xenlibs-rpath,$(1)) \
+    $(foreach lib,$(1),-L$(XEN_ROOT)/tools/libs/$(lib))
+endef
+
 define LIB_defs
  FILENAME_$(1) ?= xen$(1)
  XEN_libxen$(1) = $$(XEN_ROOT)/tools/libs/$(1)

tools/golang/xenlight/Makefile

@@ -27,7 +27,7 @@ GOXL_GEN_FILES = types.gen.go helpers.gen.go
 # so that it can find the actual library.
 .PHONY: build
 build: xenlight.go $(GOXL_GEN_FILES)
-	CGO_CFLAGS="$(CFLAGS_libxenlight) $(CFLAGS_libxentoollog) $(APPEND_CFLAGS)" CGO_LDFLAGS="$(LDLIBS_libxenlight) $(LDLIBS_libxentoollog) -L$(XEN_libxenlight) -L$(XEN_libxentoollog) $(APPEND_LDFLAGS)" $(GO) build -x
+	CGO_CFLAGS="$(CFLAGS_libxenlight) $(CFLAGS_libxentoollog) $(APPEND_CFLAGS)" CGO_LDFLAGS="$(call xenlibs-ldflags,light toollog) $(APPEND_LDFLAGS)" $(GO) build -x
 
 .PHONY: install
 install: build