Deprecate Makefile.

This is the first step towards getting rid of GYP configs.

R=machenbach@chromium.org

Bug: v8:7335
Change-Id: I688a9ff7a09c7cac67cfef8d74a893f2a6d00a8c
Reviewed-on: https://chromium-review.googlesource.com/876122Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50716}

Makefile

@@ -34,6 +34,11 @@ TESTFLAGS ?=
 ANDROID_NDK_HOST_ARCH ?=
 ANDROID_V8 ?= /data/local/tmp/v8
 
+$(warning Make (gyp) is deprecated. Please use GN instead.)
+$(warning See https://github.com/v8/v8/wiki/Building-with-GN)
+$(warning Or contact yangguo@chromium.org.)
+$(error Expect the Makefile to be removed soon)
+
 # Special build flags. Use them like this: "make library=shared"
 
 # library=shared || component=shared_library