refactor(ci): Correctly pass Version to Docker builds and remove Rele…

…ase Phase var (#328)

* refactor(docker): Consolidate on single Dockerfile

Also correctly pass Version & Release Phase values via ldflags to `go
build` so `spin --version` outputs correct values.

* chore(ci): Remove redundant build.sh file

Only `./Dockerfile` was calling `build.sh` and it doesn't in previous
commit.

Future CI jobs can run `go build` directly supplying OS & ARCH matrix and
LDFLAGS.

For local development we can simply run `go build`.

* refactor(build): Remove Release Phase and only use Version

`Version` is SemVer so we can add release candidate and other
designations as required.

Continue to use `dev` as default version, overridable by building with
ldflag set.

Dockerfile

@@ -4,7 +4,10 @@ ARG VERSION
 WORKDIR /app
 COPY ./ ./
 
-RUN ./build.sh --go-os linux --go-arch amd64 --version "${VERSION:-}"
+ENV LD_VERSION="-X github.com/spinnaker/spin/version.Version=${VERSION}"
+
+RUN GOARCH=amd64 GOOS=linux CGO_ENABLED=0 go build \
+    -ldflags "${LD_VERSION}" .
 
 FROM alpine
 

version/version.go

@@ -14,25 +14,13 @@
 
 package version
 
-import (
-	"fmt"
-)
-
 // Main version number being run right now.
-var Version = ""
-
-// A pre-release marker for the version. If this is an empty string,
-// then the release is a final release. Otherwise this is a pre-release
-// version e.g. "dev", "alpha", etc.
-var ReleasePhase = "dev"
+var Version = "dev"
 
 // User Agent name set in requests.
 const UserAgent = "Spin-CLI"
 
 // String prints the version of the Spin CLI.
 func String() string {
-	if ReleasePhase != "" {
-		return fmt.Sprintf("%s-%s", Version, ReleasePhase)
-	}
 	return Version
 }