Fix compiler flags on Android/ARM:  - generate position-independent code (PIE), a requirement to run binaries on Android 5.0+ devices;  - correctly handle EIGEN_TEST_FMA + EIGEN_TEST_NEON to pass -mfpu=neon-vfpv4.
Fix compiler flags on Android/ARM:
 - generate position-independent code (PIE), a requirement to run binaries on Android 5.0+ devices;
 - correctly handle EIGEN_TEST_FMA + EIGEN_TEST_NEON to pass -mfpu=neon-vfpv4.

rotorliu/eigen,madlib/eigen_backup,madlib/eigen_backup,rotorliu/eigen,madlib/eigen_backup,rotorliu/eigen,madlib/eigen_backup,rotorliu/eigen