When compiling manifests, filter out remarks emitted by new Swift compiler driver (#3290)

* Temporary workaround to filter out remarks emitted by Swift compiler driver in newer toolchains.  This remark is temporary, but is causing spurious test failures for tests that make sure there are no diagnostics.

* Add Radar number to comment about temporary workaround.

Author: abertelrud

Sources/PackageLoading/ManifestLoader.swift

@@ -513,7 +513,10 @@ public final class ManifestLoader: ManifestLoaderProtocol {
         // We might have some non-fatal output (warnings/notes) from the compiler even when
         // we were able to parse the manifest successfully.
         if let compilerOutput = result.compilerOutput {
-            diagnostics?.emit(.warning(ManifestLoadingDiagnostic(output: compilerOutput, diagnosticFile: result.diagnosticFile)))
+            // FIXME: Temporary workaround to filter out debug output from integrated Swift driver. [rdar://73710910]
+            if !(compilerOutput.hasPrefix("<unknown>:0: remark: new Swift driver at") && compilerOutput.hasSuffix("will be used")) {
+                diagnostics?.emit(.warning(ManifestLoadingDiagnostic(output: compilerOutput, diagnosticFile: result.diagnosticFile)))
+            }
         }
 
         return parsedManifest