Revert "Revert "Build support for 32-bit armv8-a""

This reverts commit 7de79cbe.

Fixed CTS build issue by adding -march=armv7-a in cts/tests/tests/os/jni/Android.mk since the library built here needs/uses instruction (swp) obsolete in ARMv8.

Bug: 64964151
Test: lunch aosp_arm64-userdebug; make -j cts
      lunch aosp_x86-userdebug; make -j cts
      lunch aosp_sailfish-userdebug; make -j cts
      lunch aosp_bullhead-userdebug; make -j cts

Change-Id: Ic3a121600da8e2a9a2d5176b9680cd18ce457959