message: Cache tsconfig when generating per-file cache key.
diff: @@ -78,6 +78,7 @@ export function process(
  return src;
  }
  +let tsConfig = undefined;
  export function getCacheKey(
  fileData: string,
  filePath: Path,
  @@ -85,7 +86,9 @@ export function getCacheKey(
  options: TransformOptions = { instrument: false }): string {
  const jestConfig: JestConfig = JSON.parse(configStr);
  - const tsConfig = getTSConfig(jestConfig.globals, options.instrument);
  + if (!tsConfig) {
  + tsConfig = getTSConfig(jestConfig.globals, options.instrument);
  + }
  return crypto.createHash('md5')
  .update(JSON.stringify(tsConfig), 'utf8')
  