Unlock -profile-generate for WebAssembly targets

We added support for `-profile-generate` in the latest LLVM, but it is
explicitly banned for WebAssembly targets now. Unlock the feature by
adding the necessary runtime library to the link command line as well as
other platforms.

Author: kateinoigakukun

Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift

@@ -160,8 +160,11 @@ extension WebAssemblyToolchain {
         throw Error.sanitizersUnsupportedForTarget(targetTriple.triple)
       }
 
-      guard !parsedOptions.hasArgument(.profileGenerate) else {
-        throw Error.profilingUnsupportedForTarget(targetTriple.triple)
+      if parsedOptions.hasArgument(.profileGenerate) {
+        let libProfile = VirtualPath.lookup(targetInfo.runtimeResourcePath.path)
+          .appending(components: "clang", "lib", targetTriple.osName,
+                                 "libclang_rt.profile-\(targetTriple.archName).a")
+        commandLine.appendPath(libProfile)
       }
 
       if let lto = lto {

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -4463,6 +4463,27 @@ final class SwiftDriverTests: XCTestCase {
     }
     #endif
 
+    // -profile-generate should add libclang_rt.profile for WebAssembly targets
+    try withTemporaryDirectory { resourceDir in
+      try localFileSystem.writeFileContents(resourceDir.appending(components: "wasi", "static-executable-args.lnk")) {
+        $0.send("garbage")
+      }
+
+      for triple in ["wasm32-unknown-wasi", "wasm32-unknown-wasip1-threads"] {
+        var driver = try Driver(args: [
+          "swiftc", "-profile-generate", "-target", triple, "test.swift",
+          "-resource-dir", resourceDir.pathString
+        ])
+        let plannedJobs = try driver.planBuild().removingAutolinkExtractJobs()
+
+        XCTAssertEqual(plannedJobs.count, 2)
+        XCTAssertEqual(plannedJobs[0].kind, .compile)
+
+        XCTAssertEqual(plannedJobs[1].kind, .link)
+        XCTAssert(plannedJobs[1].commandLine.containsPathWithBasename("libclang_rt.profile-wasm32.a"))
+      }
+    }
+
     for explicitUseLd in [true, false] {
       var args = ["swiftc", "-profile-generate", "-target", "x86_64-unknown-windows-msvc", "test.swift"]
       if explicitUseLd {