fdo#70393: move sane and twain to subdirs of external

Change-Id: I0876c3295416abb704ca455bdd61881ff54a0285
Reviewed-on: https://gerrit.libreoffice.org/6568
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>

RepositoryExternal.mk

@@ -162,7 +162,7 @@ ifeq (SANE,$(filter SANE,$(BUILD_TYPE)))
 
 define gb_LinkTarget__use_sane_headers
 $(call gb_LinkTarget_set_include,$(1),\
-	-I$(SRCDIR)/$(if $(filter WNT,$(OS)),twain,sane)/inc \
+	-I$(SRCDIR)/external/$(if $(filter WNT,$(OS)),twain,sane)/inc \
 	$$(INCLUDE) \
 )