Work around "xargs: environment is too large for exec" errors on Windows

...when e.g. doing 'make sal.clean'

Change-Id: I63c13dd010cf8d24f9548cf2fe089067381a4efe
Reviewed-on: https://gerrit.libreoffice.org/43948Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

solenv/gbuild/LinkTarget.mk

@@ -538,7 +538,7 @@ $(WORKDIR)/Clean/LinkTarget/% :
 		$(call gb_LinkTarget_get_objects_list,$(LINKTARGET)) \
 		$(ILIBTARGET) \
 		$(AUXTARGETS)) && \
-		cat $${RESPONSEFILE} /dev/null | xargs -n 200 rm -fr && \
+		cat $${RESPONSEFILE} /dev/null | $(if $(filter WNT,$(OS)),env -i PATH="$$PATH") xargs -n 200 rm -fr && \
 		rm -f $${RESPONSEFILE}