Only install to $OUT/apex for installable apexes

When coverage is enabled there are two variants of the apex, one
installable and one not installable.  Don't try to install files
files to $OUT/apex for the non-installable variant.

Bug: 217453046
Test: m NATIVE_COVERAGE_PATHS="*" NATIVE_COVERAGE_EXCLUDE_PATHS="art bionic/libc device" CLANG_COVERAGE=true USE_HOST_MUSL=true com.android.runtime
Change-Id: I23e58c811ff943b9d5dec025fa619c8db835b29c