chore: make the build flexible

Changes the behavior of `build.ts` by using two new environment
variables: BUILD_TARGET and RELEASE_VERSION.

BUILD_TARGET must be one of the targets supported by deno.

RELEASE_VERSION string used for naming the resulting binaries.

Example:

  BUILD_TARGET=x86_64-unknown-linux-gnu \
  RELEASE_VERSION=v0.1.0 \
  deno run ... build.ts

If the variables don’t exist, `build.ts` builds a binary based on runtime in use.

cli/build.ts

@@ -2,7 +2,6 @@ import { bundle } from "https://deno.land/x/buckets@0.1.0/mod.ts";
 import * as esbuild from "https://deno.land/x/esbuild@v0.12.19/mod.js";
 
 import conf from "./buckets.ts";
-import { PIPELINIT_VERSION } from "./deps.ts";
 
 const TARGETS = [
   "x86_64-unknown-linux-gnu",
@@ -11,6 +10,24 @@ const TARGETS = [
   "aarch64-apple-darwin",
 ];
 
+const target: string | undefined = Deno.env.get("BUILD_TARGET");
+const version: string | undefined = Deno.env.get("RELEASE_VERSION");
+
+if (target && !TARGETS.includes(target)) {
+  console.error(
+    `Invalid build target '${target}'. Must be one of:`,
+  );
+  console.error(TARGETS.join("\n"));
+  Deno.exit(1);
+}
+
+if (target && !version) {
+  console.error(
+    "The environment variable RELEASE_VERSION must be defined if BUILD_TARGET is also defined",
+  );
+  Deno.exit(1);
+}
+
 // Bundle and minify
 await bundle(conf);
 const beforeMinify = await Deno.readTextFile(conf.output);
@@ -20,20 +37,20 @@ const result = await esbuild.transform(beforeMinify, {
 await Deno.writeTextFile(conf.output, result.code);
 esbuild.stop();
 
-const compile = async function (target?: string) {
+const compile = async function (target?: string, version?: string) {
   const cmd = [
     "deno",
     "compile",
     "--unstable",
     "--allow-read=.",
     "--allow-write",
   ];
-  if (target) {
+  if (target && version) {
     cmd.push(
       "--target",
       target,
       "--output",
-      `bin/pipelinit-${PIPELINIT_VERSION}-${target}`,
+      `bin/pipelinit-${version}-${target}`,
     );
   } else {
     cmd.push("--output", "bin/pipelinit");
@@ -47,14 +64,14 @@ const compile = async function (target?: string) {
   }
 };
 
-const tar = async function (target: string) {
+const tar = async function (target: string, version: string) {
   const p = Deno.run({
     cwd: "bin",
     cmd: [
       "tar",
       "-czf",
-      `pipelinit-${PIPELINIT_VERSION}-${target}.tar.gz`,
-      `pipelinit-${PIPELINIT_VERSION}-${target}`,
+      `pipelinit-${version}-${target}.tar.gz`,
+      `pipelinit-${version}-${target}`,
     ],
   });
 
@@ -64,14 +81,14 @@ const tar = async function (target: string) {
   }
 };
 
-const zip = async function (target: string) {
+const zip = async function (target: string, version: string) {
   const p = Deno.run({
     cwd: "bin",
     cmd: [
       "zip",
       "-9",
-      `pipelinit-${PIPELINIT_VERSION}-${target}.zip`,
-      `pipelinit-${PIPELINIT_VERSION}-${target}.exe`,
+      `pipelinit-${version}-${target}.zip`,
+      `pipelinit-${version}-${target}.exe`,
     ],
   });
 
@@ -81,18 +98,18 @@ const zip = async function (target: string) {
   }
 };
 
-const compress = async function (target: string) {
+const compress = async function (target: string, version: string) {
   if (target === "x86_64-pc-windows-msvc") {
-    await zip(target);
+    await zip(target, version);
   } else {
-    await tar(target);
+    await tar(target, version);
   }
 };
 
-await compile();
-for (const target of TARGETS) {
-  await compile(target);
-  await compress(target);
+await compile(target, version);
+
+if (target && version) {
+  await compress(target, version);
 }
 
 await Deno.remove(conf.output);