From 2a7b2fd37e52dbeeca2d7bdee1897a4e060e2564 Mon Sep 17 00:00:00 2001
From: Tim Hockin <thockin@google.com>
Date: Thu, 2 Jun 2016 21:47:34 -0700
Subject: [PATCH] Tighten up Makefile

Default SHELL and some other variables for max correctness.
---
 Makefile | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 4cb737befed..f6f0b52e1fa 100644
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# It's necessary to set this because some docker images don't make sh -> bash.
+SHELL := /bin/bash
+
+# We don't need make's built-in rules.
+MAKEFLAGS += --no-builtin-rules --warn-undefined-variables
+.SUFFIXES:
+
 # Old-skool build tools.
 #
 # Targets (see each target for more information):
@@ -20,15 +27,17 @@
 #   test: Run tests.
 #   clean: Clean up.
 
-OUT_DIR = _output
+OUT_DIR ?= _output
 BIN_DIR := $(OUT_DIR)/bin
 PRJ_SRC_PATH := k8s.io/kubernetes
 GENERATED_FILE_PREFIX := zz_generated.
 MAKE_METAFILE_PREFIX := .make.
 
+GOFLAGS ?=
 KUBE_GOFLAGS = $(GOFLAGS)
 export KUBE_GOFLAGS
 
+GOLDFLAGS ?=
 KUBE_GOLDFLAGS = $(GOLDFLAGS)
 export KUBE_GOLDFLAGS