Consume per-runtime language servers

To keep our package size more manageable, we now create a separate
language server package per runtime.

server/ServerDownload.csproj

@@ -20,7 +20,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageDownload Include="Microsoft.CodeAnalysis.LanguageServer" version="[$(MicrosoftCodeAnalysisLanguageServerVersion)]" />
+        <PackageDownload Include="$(PackageName)" version="[$(PackageVersion)]" />
     </ItemGroup>
 
 </Project>

tasks/offlinePackagingTasks.ts

@@ -76,7 +76,6 @@ gulp.task('installDependencies', async () => {
 // Install Tasks
 async function installRoslyn(packageJSON: any, platformInfo?: PlatformInformation) {
     const roslynVersion = packageJSON.defaults.roslyn;
-    const packagePath = await acquireNugetPackage('Microsoft.CodeAnalysis.LanguageServer', roslynVersion);
 
     // Find the matching server RID for the current platform.
     let serverPlatform: string;
@@ -90,6 +89,11 @@ async function installRoslyn(packageJSON: any, platformInfo?: PlatformInformatio
         )!.rid;
     }
 
+    const packagePath = await acquireNugetPackage(
+        `Microsoft.CodeAnalysis.LanguageServer.${serverPlatform}`,
+        roslynVersion
+    );
+
     // Get the directory containing the server executable for the current platform.
     const serverExecutableDirectory = path.join(packagePath, 'content', 'LanguageServer', serverPlatform);
     if (!fs.existsSync(serverExecutableDirectory)) {
@@ -150,7 +154,8 @@ async function acquireNugetPackage(packageName: string, packageVersion: string):
     const dotnetArgs = [
         'restore',
         path.join(rootPath, 'server'),
-        `/p:MicrosoftCodeAnalysisLanguageServerVersion=${packageVersion}`,
+        `/p:PackageName=${packageName}`,
+        `/p:PackageVersion=${packageVersion}`,
     ];
     if (argv.interactive) {
         dotnetArgs.push('--interactive');