sandbox: Allow link flags to be given

At present the link flags are not used for sandbox. Update the command
line to use them.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/config.mk

@@ -16,7 +16,7 @@ PLATFORM_CPPFLAGS += $(shell $(SDL_CONFIG) --cflags)
 endif
 
 cmd_u-boot__ = $(CC) -o $@ -Wl,-T u-boot.lds $(u-boot-init) \
-	$(LTO_FINAL_LDFLAGS) \
+	$(KBUILD_LDFLAGS:%=-Wl,%)$(LTO_FINAL_LDFLAGS) \
 	-Wl,--whole-archive \
 		$(u-boot-main) \
 		$(u-boot-keep-syms-lto) \
@@ -24,7 +24,7 @@ cmd_u-boot__ = $(CC) -o $@ -Wl,-T u-boot.lds $(u-boot-init) \
 	$(PLATFORM_LIBS) -Wl,-Map -Wl,u-boot.map
 
 cmd_u-boot-spl = (cd $(obj) && $(CC) -o $(SPL_BIN) -Wl,-T u-boot-spl.lds \
-	$(LTO_FINAL_LDFLAGS) \
+	$(KBUILD_LDFLAGS:%=-Wl,%) $(LTO_FINAL_LDFLAGS) \
 	$(patsubst $(obj)/%,%,$(u-boot-spl-init)) \
 	-Wl,--whole-archive \
 		$(patsubst $(obj)/%,%,$(u-boot-spl-main)) \