Add system shared libs to a prebuilt_internal.mk path

This commit adds LOCAL_SYSTEM_SHARED_LIBRARIES to a
`prebuilt_internal.mk` path.

Before this commit, LOCAL_SYSTEM_SHARED_LIBRARIES is only supported when
LOCAL_STRIP_MODULE is specified. If LOCAL_STRIP_MODULE is not specified,
default system shared libs (libc, libdl, and libm) are not added
implicitly. This commit makes both paths have the same behavior.

See also. https://android-review.googlesource.com/814993

Bug: 119086738
Test: CHECK_ELF_FILES=true make -j check-elf-files
Change-Id: I84ff9f6157ad6e5ee26234133fb7148a3e2b9551