Filter codesign messages

Right now we end up with this output on relink:

```
/Users/neonacho/Projects/public/swift-package-manager/.build/arm64-apple-macosx/debug/swift-bootstrap: replacing existing signature
```

This change specifically filters any output from `codesign` commands which haven't failed and we aren't in verbose mode.

This should eventually be possible at the command level, but for the time being this allows us to avoid shipping SwiftPM with this messy output.

rdar://118937939

Author: neonichu

Sources/Build/BuildOperationBuildSystemDelegateHandler.swift

@@ -826,8 +826,10 @@ final class BuildOperationBuildSystemDelegateHandler: LLBuildBuildSystemDelegate
         process: ProcessHandle,
         result: CommandExtendedResult
     ) {
+        // FIXME: This should really happen at the command-level and is just a stopgap measure.
+        let shouldFilterOutput = !self.logLevel.isVerbose && command.verboseDescription.components(separatedBy: " ").first == "codesign" && result.result != .failed
         queue.async {
-            if let buffer = self.nonSwiftMessageBuffers[command.name] {
+            if let buffer = self.nonSwiftMessageBuffers[command.name], !shouldFilterOutput {
                 self.progressAnimation.clear()
                 self.outputStream.send(buffer)
                 self.outputStream.flush()