fix: select musl JDK artifacts on Alpine for five distributions (#1220)

On Alpine, `getPlatformOption()` returned the glibc platform key for
Dragonwell, Corretto, Zulu, Liberica and Liberica NIK, so the action
resolved and installed a glibc JDK that cannot run under musl.

Add a shared `isAlpineLinux()` helper and use it to select each vendor's
musl artifacts:

| distribution | glibc         | musl           |
| ------------ | ------------- | -------------- |
| Dragonwell   | `linux`       | `alpine-linux` |
| Corretto     | `linux`       | `alpine`       |
| Zulu         | `linux_glibc` | `linux_musl`   |
| Liberica     | `linux`       | `linux-musl`   |
| Liberica NIK | `linux`       | `linux-musl`   |

Each key was verified against the vendor's live metadata API or manifest.

There is deliberately no silent fallback to glibc when a vendor has no
musl build for the requested version or architecture: the existing "could
not find a version that satisfies" error fires instead. This matches the
behaviour Temurin and SapMachine already have, and a glibc JDK would not
run on musl anyway.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 74248bb0-72af-41d8-b85d-b0f5836e68db

src/distributions/dragonwell/installer.ts

@@ -15,6 +15,7 @@ import {
   renameWinArchive
 } from '../../util.js';
 import {IDragonwellVersions, IDragonwellAllVersions} from './models.js';
+import {isAlpineLinux} from '../platform-types.js';
 import {
   JavaDownloadRelease,
   JavaInstallerOptions,
@@ -202,6 +203,8 @@ export class DragonwellDistribution extends JavaBase {
     switch (process.platform) {
       case 'win32':
         return 'windows';
+      case 'linux':
+        return isAlpineLinux() ? 'alpine-linux' : 'linux';
       default:
         return process.platform;
     }