Copy generated xml file for NDK api coverage to dist when CLANG_COVERAGE flag set.

Test: build/soong/soong_ui.bash --make-mode SKIP_ABI_CHECKS=true TARGET_PRODUCT=aosp_cf_x86_phone TARGET_BUILD_VARIANT=userdebug droid dist DIST_DIR=/usr/local/google/home/sophiez/my_dist_dir EMMA_INSTRUMENT=true EMMA_INSTRUMENT_FRAMEWORK=true CLANG_COVERAGE=true SKIP_BOOT_JARS_CHECK=true tests

Change-Id: I778da9ca7897752274744eca5530412c146fac96