Force removal of UNZIP_DIR when unpacking zip (gbuild).

mv only moves non-hidden files out of UNZIP_DIR, hence removal of
UNZIP_DIR can fail if there are hidden files remaining. This assumes
that hidden files aren't actually needed for our purposes.

This is a problem e.g. for libatomic_ops which contains a .gitignore
in it's top directory, causing the removal of UNZIP_DIR to fail.

Change-Id: Ia4a621b90bc4cc5fc15dd2a3ecc209734abc6269
Reviewed-on: https://gerrit.libreoffice.org/5808Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>

solenv/gbuild/UnpackedTarball.mk

@@ -44,7 +44,7 @@ unzip \
 $(if $(filter-out 0,$(UNPACKED_STRIP_COMPONENTS)),\
 	&& UNZIP_DIR=`ls $(UNPACKED_DIR)` \
 	&& mv $(UNPACKED_DIR)/$$UNZIP_DIR/* $(UNPACKED_DIR) \
-	&& rmdir $(UNPACKED_DIR)/$$UNZIP_DIR \
+	&& rm -rf $(UNPACKED_DIR)/$$UNZIP_DIR \
 )
 endef