run the sum generation in the release script instead of build

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

script/build

@@ -16,5 +16,3 @@ fi
 docker build -t docker-machine .
 rm -f docker-machine*
 docker run --rm -v `pwd`:/go/src/github.com/docker/machine docker-machine gox "${OS_PLATFORM_ARG[@]}" "${OS_ARCH_ARG[@]}" -output="docker-machine_{{.OS}}-{{.Arch}}" -ldflags="-w -X github.com/docker/machine/version.GITCOMMIT `git rev-parse --short HEAD`"
-
-exec docker run --rm -v `pwd`:/go/src/github.com/docker/machine docker-machine ./script/generate-sums

script/release

@@ -31,3 +31,4 @@ for BINARY in docker-machine_*; do
         --file $BINARY
 done
 
+docker run --rm -v `pwd`:/go/src/github.com/docker/machine docker-machine ./script/generate-sums