Error: 前言中不允许有内容

:app:mergeDebugResources
Putting task artifact state for task ':app:mergeDebugResources' into context took 0.0 secs.
Executing task ':app:mergeDebugResources' (up-to-date check took 0.093 secs) due to:
  Task has failed previously.
All input files are considered out-of-date for incremental task ':app:mergeDebugResources'.
Unable do incremental execution: full task run
/Users/feng/work/demo/app/build/intermediates/exploded-aar/com.xxx.xxx/xxxx/1.0.7-SNAPSHOT/res/font/xxx.ttf:1:1: Error: 前言中不允许有内容。
:app:mergeDebugR

com.android.tools.build:gradle:4.1.3 升级到3.1.x就没问题了