Pass version number to build-chocolatey and update-homebrew

Instead of always grabbing the Yarn version number from yarnpkg.com, allow it to be passed in as command line argument.
Updates Jenkins bump-version job to pass it in.

References yarnpkg/website#471

jenkins_jobs.groovy

@@ -33,6 +33,17 @@ job('yarn-version') {
       branch 'origin', 'master'
       pushOnlyIfSuccess
     }
+    downstreamParameterized {
+      // Other jobs to run when version number is bumped
+      trigger([
+        'yarn-chocolatey',
+        'yarn-homebrew',
+      ]) {
+        parameters {
+          currentBuild()
+        }
+      }
+    }
     gitHubIssueNotifier {
     }
   }
@@ -71,16 +82,15 @@ job('yarn-chocolatey') {
   scm {
     github 'yarnpkg/yarn', 'master'
   }
-  triggers {
-    upstream 'yarn-version'
+  parameters {
+    stringParam 'YARN_VERSION'
   }
   steps {
     powerShell '.\\scripts\\build-chocolatey.ps1 -Publish'
   }
   publishers {
     gitHubIssueNotifier {
     }
-    mailer '[email protected]'
   }
 }
 
@@ -90,15 +100,14 @@ job('yarn-homebrew') {
   scm {
     github 'yarnpkg/yarn', 'master'
   }
-  triggers {
-    upstream 'yarn-version'
+  parameters {
+    stringParam 'YARN_VERSION'
   }
   steps {
     shell './scripts/update-homebrew.sh'
   }
   publishers {
     gitHubIssueNotifier {
     }
-    mailer '[email protected]'
   }
 }

scripts/build-chocolatey.ps1

@@ -7,7 +7,15 @@ param(
 
 $ErrorActionPreference = 'Stop'; # stop on all errors
 
-$latest_version = [String](Invoke-WebRequest -Uri https://yarnpkg.com/latest-version -UseBasicParsing)
+# See if YARN_VERSION was passed in the environment, otherwise get version
+# number from Yarn site
+if ($Env:YARN_VERSION) {
+  $latest_version = $Env:YARN_VERSION
+} else {
+  Write-Output 'Getting Yarn version from https://yarnpkg.com/latest-version'
+  $latest_version = [String](Invoke-WebRequest -Uri https://yarnpkg.com/latest-version -UseBasicParsing)
+}
+
 $latest_chocolatey_version = (Find-Package -Name Yarn).Version
 
 if ([Version]$latest_chocolatey_version -ge [Version]$latest_version) {

scripts/update-homebrew.sh

@@ -3,7 +3,14 @@
 
 set -ex
 
-version=`curl --fail https://yarnpkg.com/latest-version`
+# See if YARN_VERSION was passed in the environment, otherwise get version
+# number from Yarn site
+if [ -z "$YARN_VERSION" ]; then
+  echo 'Getting Yarn version from https://yarnpkg.com/latest-version'
+  version=`curl --fail https://yarnpkg.com/latest-version`
+else
+  version="$YARN_VERSION"
+fi
 
 # Ensure Linuxbrew is on the PATH
 PATH=$PATH:$HOME/.linuxbrew/bin/