Merge "Make FlexLexer buildable for native_bridge" am: 6d1df66700 am: e8be11c9e7 am: 3b0bf4a3e2

Original change: https://android-review.googlesource.com/c/platform/external/eigen/+/1308019

Change-Id: I1e84825184a0b242ffb1b152f8e45336af9bf448