Add llvm-objcopy to android_sdk_repo_host's implicit tools

llvm-strip is actually a symlink to llvm-objcopy. Since aosp/2850015,
rules must add both the symlink and the target of the symlink to
the sandbox to avoid a dangling symlink.

Fixes: 314994282
Test: m sdk sdk_repo dist
Change-Id: I72494596f3597e176222a44c822d0b12cdd4cde4