Merge "Make FlexLexer buildable for native_bridge" am: 6d1df66700 am: e8be11c9e7 am: 3b0bf4a3e2 am: 5c0fb165b4

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

Change-Id: I70f95ec9912a77129258999fa192337cc6096b3a