build: fix api guardian path for windows (angular#26888)

At the moment, `path.posix.relative` will break paths in windows as it will return something like
```
Error: Source file "../C:/users/alag/_bazel_alag/3tbqurya/execroot/angular/bazel-out/x64_windows-fastbuild/bin/packages/core/core.d.ts" not found
```

PR Close angular#26888

Author: alan-agius4

tools/ts-api-guardian/lib/cli.ts

@@ -191,7 +191,7 @@ function resolveBazelFilePath(fileName: string): string {
   // are not available in the working directory. In order to resolve the real path for the
   // runfile, we need to use `require.resolve` which handles runfiles properly on Windows.
   if (process.env['BAZEL_TARGET']) {
-    return path.posix.relative(process.cwd(), require.resolve(fileName));
+    return path.relative(process.cwd(), require.resolve(fileName));
   }
 
   return fileName;