Set up Windows environment with build tools.

src/main.ts

@@ -4,6 +4,7 @@ import * as graalvm from './graalvm'
 import {join} from 'path'
 import {mkdirP} from '@actions/io'
 import {setUpGraalVMTrunk} from './graalvm-trunk'
+import {setUpWindowsEnvironment} from './msvc'
 
 async function run(): Promise<void> {
   try {
@@ -14,6 +15,10 @@ async function run(): Promise<void> {
       componentsString.length > 0 ? componentsString.split(',') : []
     const setJavaHome = core.getInput('set-java-home') === 'true'
 
+    if (c.IS_WINDOWS) {
+      setUpWindowsEnvironment()
+    }
+
     await mkdirP(c.GRAALVM_BASE)
 
     // Download or build GraalVM

src/msvc.ts

@@ -0,0 +1,60 @@
+import * as core from '@actions/core'
+import {execSync} from 'child_process'
+import {existsSync} from 'fs'
+
+// Keep in sync with https://github.com/actions/virtual-environments
+const KNOWN_VISUAL_STUDIO_INSTALLATIONS = [
+  'C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Enterprise', // 'windows-2016'
+  'C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Enterprise', // 'windows-2019' and 'windows-latest'
+  'C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise' // 'windows-2022'
+]
+const VCVARSALL_SUBPATH = '\\VC\\Auxiliary\\Build\\vcvarsall.bat'
+
+function findVcvarsallPath(): string {
+  for (const installation of KNOWN_VISUAL_STUDIO_INSTALLATIONS) {
+    const candidate = `${installation}${VCVARSALL_SUBPATH}`
+    if (existsSync(candidate)) {
+      return candidate
+    }
+  }
+  throw new Error('Failed to find vcvarsall.bat')
+}
+
+export function setUpWindowsEnvironment(): void {
+  core.startGroup('Updating Windows environment...')
+
+  const vcvarsallPath = findVcvarsallPath()
+  core.debug(`Calling "${vcvarsallPath}"...`)
+  const [originalEnv, vcvarsallOutput, updatedEnv] = execSync(
+    `set && cls && "${vcvarsallPath}" x64 && cls && set`,
+    {shell: 'cmd'}
+  )
+    .toString()
+    .split('\f') // form feed page break (printed by `cls`)
+  core.debug(vcvarsallOutput)
+
+  const originalEnvMap = new Map<string, string>()
+  for (const line of originalEnv.split('\r\n')) {
+    if (line.includes('=')) {
+      const [name, value] = line.split('=')
+      originalEnvMap.set(name, value)
+    } else if (line) {
+      core.debug(`Skipping ${line} (does not include '=')...`)
+    }
+  }
+
+  for (const line of updatedEnv.split('\r\n')) {
+    if (line.includes('=')) {
+      const [name, value] = line.split('=')
+      const originalValue = originalEnvMap.get(name)
+      if (value !== originalValue) {
+        core.exportVariable(name, value)
+        core.debug(`"${name}" set to "${value}"`)
+      }
+    } else if (line) {
+      core.debug(`Skipping ${line} (does not include '=')...`)
+    }
+  }
+
+  core.endGroup()
+}