build: re-enable building outside gopath

Have build return an error code if build fails and add a test to travis
to confirm running build outside the gopath works.

.travis.yml

@@ -54,6 +54,7 @@ script:
         GOARCH=386 PASSES="build unit" ./test
         ;;
       *)
-        GOARCH="${TARGET}" ./build
+        # test building out of gopath
+        GO_BUILD_FLAGS="-a -v" GOPATH=/bad-go-path GOARCH="${TARGET}" ./build
         ;;
     esac

build

@@ -1,8 +1,5 @@
 #!/bin/sh -e
 
-CDIR=$(cd `dirname "$0"` && pwd)
-cd "$CDIR"
-
 # set some environment variables
 ORG_PATH="github.com/coreos"
 REPO_PATH="${ORG_PATH}/etcd"
@@ -34,11 +31,13 @@ etcd_build() {
 	if [ -n "${BINDIR}" ]; then out="${BINDIR}"; fi
 	toggle_failpoints
 	# Static compilation is useful when etcd is run in a container
-	CGO_ENABLED=0 go build $GO_BUILD_FLAGS -installsuffix cgo -ldflags "-s -X ${REPO_PATH}/cmd/vendor/${REPO_PATH}/version.GitSHA=${GIT_SHA}" -o ${out}/etcd ${REPO_PATH}/cmd/etcd
-	CGO_ENABLED=0 go build $GO_BUILD_FLAGS -installsuffix cgo -ldflags "-s" -o ${out}/etcdctl ${REPO_PATH}/cmd/etcdctl
+	CGO_ENABLED=0 go build $GO_BUILD_FLAGS -installsuffix cgo -ldflags "-s -X ${REPO_PATH}/cmd/vendor/${REPO_PATH}/version.GitSHA=${GIT_SHA}" -o ${out}/etcd ${REPO_PATH}/cmd/etcd || return
+	CGO_ENABLED=0 go build $GO_BUILD_FLAGS -installsuffix cgo -ldflags "-s" -o ${out}/etcdctl ${REPO_PATH}/cmd/etcdctl || return
 }
 
 etcd_setup_gopath() {
+	CDIR=$(cd `dirname "$0"` && pwd)
+	cd "$CDIR"
 	etcdGOPATH=${CDIR}/gopath
 	# preserve old gopath to support building with unvendored tooling deps (e.g., gofail)
 	export GOPATH=${etcdGOPATH}:$GOPATH
@@ -49,5 +48,9 @@ etcd_setup_gopath() {
 
 toggle_failpoints
 
-# don't build when sourced
-(echo "$0" | grep "/build$" > /dev/null) && etcd_build || true
+# only build when called directly, not sourced
+if echo "$0" | grep "build$" >/dev/null; then
+	# force new gopath so builds outside of gopath work
+	etcd_setup_gopath
+	etcd_build
+fi