Enable LTO for riscv64

This partially reverts commit 1281b994.

Bug: b/282584808, b/254713216

Reason for revert: LTO can be enabled as emultated tls is now globally disabled https://android-review.git.corp.google.com/c/platform/build/soong/+/2431153

Change-Id: I66c83b1116550179043490a11f66b8630c0e6b1b