kbuild: call export_report from the Makefile

The main feature is that export_report now automatically works
for O= builds.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

Makefile

@@ -1157,6 +1157,7 @@ help:
 	@echo  'Static analysers'
 	@echo  '  checkstack      - Generate a list of stack hogs'
 	@echo  '  namespacecheck  - Name space analysis on compiled kernel'
+	@echo  '  export_report   - List the usages of all exported symbols'
 	@if [ -r $(srctree)/include/asm-$(SRCARCH)/Kbuild ]; then \
 	 echo  '  headers_check   - Sanity check on exported headers'; \
 	 fi
@@ -1421,6 +1422,9 @@ versioncheck:
 namespacecheck:
 	$(PERL) $(srctree)/scripts/namespace.pl
 
+export_report:
+	$(PERL) $(srctree)/scripts/export_report.pl
+
 endif #ifeq ($(config-targets),1)
 endif #ifeq ($(mixed-targets),1)