add option to specify number of jobs for build command

src/cmds.ts

@@ -29,6 +29,18 @@ export const commands: Cmd[] = [
         description:
           "Doesn't check to see if all of the patches have been applied",
       },
+      {
+        arg: "-j, --jobs <number>",
+        description:
+          'Number of jobs to run in parallel. Defaults to the number of cores on your machine.',
+        parse: (val: string) => {
+          const parsed = parseInt(val, 10)
+          if (isNaN(parsed)) {
+            throw new Error('Invalid number of jobs')
+          }
+          return parsed
+        }
+      }
     ],
     requestController: async () => (await import('./commands/build')).build,
   },

src/commands/build.ts

@@ -110,7 +110,7 @@ const applyConfig = async (os: string) => {
   writeFileSync(join(ENGINE_DIR, 'browser/config/version_display.txt'), version)
 }
 
-const genericBuild = async (os: string, fast = false): Promise<boolean> => {
+const genericBuild = async (os: string, fast = false, jobs: number): Promise<boolean> => {
   log.info(`Building for "${os}"...`)
 
   log.warning(
@@ -123,6 +123,10 @@ const genericBuild = async (os: string, fast = false): Promise<boolean> => {
     buildOptions.push('faster')
   }
 
+  if (jobs) {
+    buildOptions.push(`-j${jobs}`)
+  }
+
   log.debug(`Running with build options ${buildOptions.join(', ')}`)
   log.debug(`Mach exists: ${existsSync(join(ENGINE_DIR, 'mach'))}`)
   log.debug(
@@ -156,6 +160,7 @@ const success = (date: number) => {
 
 interface Options {
   ui: boolean
+  jobs: number
   skipPatchCheck: boolean
 }
 
@@ -177,7 +182,7 @@ export const build = async (options: Options): Promise<void> => {
 
     log.info('Starting build...')
 
-    let exit = await genericBuild(prettyHost, options.ui)
+    let exit = await genericBuild(prettyHost, options.ui, options.jobs)
     process.exit(exit ? 0 : 1)
   }
 }

src/index.ts

@@ -108,7 +108,9 @@ for (const command of commands) {
 
   // Register all of the required options
   for (const opt of command?.options || []) {
-    buildCommand = buildCommand.option(opt.arg, opt.description)
+    buildCommand = opt.parse !== undefined ?
+      buildCommand.option(opt.arg, opt.description, opt.parse) :
+      buildCommand.option(opt.arg, opt.description);
   }
 
   buildCommand = buildCommand.action(async (...arguments_) => {

src/types.d.ts

@@ -25,6 +25,7 @@ export interface Cmd {
 export interface CmdOption {
   arg: string
   description: string
+  parse?: (val: string) => unknown
 }
 
 export type CmdFlagPlatform = NodeJS.Platform