Use find(1)'s -exec directly.

toybox xargs doesnt have --no-run-if-empty:

  xargs: Unknown option no-run-if-empty (see "xargs --help")

But we shouldn't need it anyway.

Test: make -j32 showcommands dist TARGET_BUILD_APPS='Launcher3 Launcher3Tests' EMMA_INSTRUMENT_STATIC=true TARGET_BUILD_VARIANT=userdebug
Change-Id: I72f680c27b58a42b9fb9de1a0bc4187cabcfb516