Add WASI as a supported target for sanitizers

We are adding support for sanitizers on WASI targets. This commit
adds driver support by unblocking hard-coded checks and forwarding
sanitizer flags to clang linker driver.

Author: kateinoigakukun

Sources/SwiftDriver/Driver/Driver.swift

@@ -2751,7 +2751,7 @@ extension Driver {
     }
 
     // Check that we're one of the known supported targets for sanitizers.
-    if !(targetTriple.isWindows || targetTriple.isDarwin || targetTriple.os == .linux) {
+    if !(targetTriple.isWindows || targetTriple.isDarwin || targetTriple.os == .linux || targetTriple.os == .wasi) {
       diagnosticEngine.emit(
         .error_unsupported_opt_for_target(
           arg: "-sanitize=",

Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift

@@ -165,8 +165,12 @@ extension WebAssemblyToolchain {
 
       // Delegate to Clang for sanitizers. It will figure out the correct linker
       // options.
-      guard sanitizers.isEmpty else {
-        throw Error.sanitizersUnsupportedForTarget(targetTriple.triple)
+      if linkerOutputType == .executable && !sanitizers.isEmpty {
+        let sanitizerNames = sanitizers
+          .map { $0.rawValue }
+          .sorted() // Sort so we get a stable, testable order
+          .joined(separator: ",")
+        commandLine.appendFlag("-fsanitize=\(sanitizerNames)")
       }
 
       if parsedOptions.hasArgument(.profileGenerate) {

Sources/SwiftDriver/Toolchains/WebAssemblyToolchain.swift

@@ -146,7 +146,7 @@ public final class WebAssemblyToolchain: Toolchain {
     targetTriple: Triple,
     isShared: Bool
   ) throws -> String {
-    throw Error.sanitizersUnsupportedForTarget(targetTriple.triple)
+    return "libclang_rt.\(sanitizer.libraryName)-\(targetTriple.archName).a"
   }
 
   public func platformSpecificInterpreterEnvironmentVariables(env: [String : String],