Work around "find: The environment is too large for exec()" errors on Windows

...similar to df9edbcd 'Work around 'xargs:
environment is too large for exec' errors on Windows"

Change-Id: I50bc5c73b84e2d8e7adc70f72f9af2d23a0b3b36
Reviewed-on: https://gerrit.libreoffice.org/60241
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

Makefile.in

@@ -224,7 +224,7 @@ distclean : clean compilerplugins-clean
         $(BUILDDIR)/instsetoo_native/util/openoffice.lst \
         $(BUILDDIR)/lo.xcent \
         $(BUILDDIR)/sysui/desktop/macosx/Info.plist
-	$(FIND) $(SRCDIR)/solenv/gdb -name \*.pyc -exec rm {} \;
+	$(if $(filter WNT,$(OS)),env -i PATH="$$PATH") $(FIND) $(SRCDIR)/solenv/gdb -name \*.pyc -exec rm {} \;
 
 #
 # custom command