Work around redirection issue on windows buildbots

with documentation build, ref #18588 (comment)
redirecting to a file should work, but redirecting to a cygwin pipe
or driving application like perl or python (in the buildbot case) doesn't

doc/Makefile

@@ -19,13 +19,19 @@ help:
 	@echo "  check     to run linkcheck and doctests"
 
 clean:
-	-rm -rf _build/* deps/*
+	-rm -rf _build/* deps/* docbuild.log
 
 cleanall: clean
 
 html:
 	@echo "Building HTML documentation."
+ifneq ($(OS),WINNT)
 	$(JULIA_EXECUTABLE) make.jl -- deploy
+else
+# work around issue #11727, windows output redirection breaking on buildbot
+	$(JULIA_EXECUTABLE) make.jl -- deploy > docbuild.log 2>&1
+	@cat docbuild.log
+endif
 	@echo "Build finished. The HTML pages are in _build/html."
 
 pdf: