Override describe to handle CoffeeScript implicit returns

CoffeeScript implicit `return`s trigger a warning since `describe` [should not](jestjs/jest#7852) `return` a value.

Cakefile

@@ -12,6 +12,7 @@ task 'generate', "Generate Jest preset JSON config.", =>
     testPathIgnorePatterns: ['node_modules', 'fixtures']
     transform: [glob]: package_json.name
     mapCoverage: true
+    setupFilesAfterEnv: ['./index']
 
   package_json.jest.transform = [glob]: './index'
   fs.writeFileSync 'package.json', JSON.stringify package_json, null, 2

index.coffee

@@ -11,3 +11,8 @@ exports.process = (source, file) =>
     presets: ['jest']
 
   compile source, { bare: true, inlineMap: true, transpile }
+
+if describe?
+  override = describe
+  # coffeelint: disable=no_backticks FIXME
+  `describe = (name, fn) => override (name, () => { fn() })`