Add osVersion parameter based on ImageOS env variable

src/setup-elixir.js

@@ -23,14 +23,15 @@ async function main() {
     elixirSpec,
     otpVersion
   )
+  const osVersion = getOSVersion()
 
   let installHex = core.getInput('install-hex')
   installHex = installHex == null ? 'true' : installHex
   let installRebar = core.getInput('install-rebar')
   installRebar = installRebar == null ? 'true' : installRebar
 
-  console.log(`##[group]Installing OTP ${otpVersion}`)
-  await installOTP(otpVersion)
+  console.log(`##[group]Installing OTP ${otpVersion} - built on ${osVersion}`)
+  await installOTP(otpVersion, osVersion)
   console.log(`##[endgroup]`)
 
   console.log(`##[group]Installing Elixir ${elixirVersion}`)
@@ -46,6 +47,7 @@ async function main() {
   console.log(`##[add-matcher]${path.join(matchersPath, 'elixir.json')}`)
   core.setOutput('otp-version', otpVersion)
   core.setOutput('elixir-version', elixirVersion)
+  core.setOutput('osVersion', osVersion)
 }
 
 function checkPlatform() {
@@ -59,6 +61,16 @@ async function getOtpVersion(spec) {
   return getVersionFromSpec(spec, await getOtpVersions()) || spec
 }
 
+function getOSVersion() {
+  const mapToUbuntuVersion = {
+    ubuntu16: 'ubuntu-16.04',
+    ubuntu18: 'ubuntu-18.04',
+    ubuntu20: 'ubuntu-20.04',
+  }
+
+  return mapToUbuntuVersion[process.env.ImageOS] || 'ubuntu-18.04'
+}
+
 exports.getElixirVersion = getElixirVersion
 
 async function getElixirVersion(spec, otpVersion) {