code: public String getOSExtensionDefinition(BootstrapConfig bootProps) {
          String osExtension = bootProps.get(BOOTPROP_OS_EXTENSIONS);
  
          if (osExtension == null) {
              String normalizedName = getNormalizedOperatingSystemName(bootProps.get("os.name"));
              osExtension = defaults.getProperty(MANIFEST_OS_EXTENSION + normalizedName);
          }
  
          if (osExtension != null)
              bootProps.put(BOOTPROP_OS_EXTENSIONS, osExtension);
  
          return osExtension;
      }
docs: Find and return the name of the os extension. Look in
  bootstrap properties first, if not explicitly defined there, get
  the default from the manifest.
  
  @return the selected log provider