RepositoryExternal.mk: missing dependency on python3 package

This was causing all these "libpython3.3m.so: file not recognized: File
truncated" failures.
(cherry picked from commit 57dd4d01)

RepositoryExternal.mk: for some reason Mac wants a GeneratedPackage
(cherry picked from commit d9162d24)

Change-Id: I5d983fee8d5cd313fbd0d6ece800fa8b80d81b35
Reviewed-on: https://gerrit.libreoffice.org/17398Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: David Ostrovsky <david@ostrovsky.org>
Reviewed-by: David Tardon <dtardon@redhat.com>

RepositoryExternal.mk

@@ -3170,6 +3170,11 @@ endef
 
 define gb_LinkTarget__use_python
 $(call gb_LinkTarget__use_python_headers,$(1))
+ifeq ($(OS),MACOSX)
+$(call gb_LinkTarget_use_generated_package,$(1),python3)
+else
+$(call gb_LinkTarget_use_package,$(1),python3)
+endif
 
 ifeq ($(OS),WNT)
 $(call gb_LinkTarget_add_libs,$(1),\

solenv/gbuild/LinkTarget.mk

@@ -1301,6 +1301,14 @@ define gb_LinkTarget_use_packages
 $(foreach package,$(2),$(call gb_LinkTarget_use_package,$(1),$(package)))
 endef
 
+# use a GeneratedPackage, possibly from another module
+# call gb_LinkTarget_use_generated_package,linktarget,package
+define gb_LinkTarget_use_generated_package
+$(call gb_LinkTarget_get_headers_target,$(1)) :| \
+	$(call gb_GeneratedPackage_get_target,$(strip $(2)))
+
+endef
+
 # Use sources from unpacked tarball of an external project
 # call gb_LinkTarget_use_unpacked,linktarget,unpackedtarget
 define gb_LinkTarget_use_unpacked