Disable LTO for libbluetooth_core_rs_bridge

Bug: 326115797
Bug: 286537287

We don't support cross-language LTO yet.  Disable LTO for
libbluetooth_core_rs_bridge since it is read by rustc (which uses
incompatible LLVM IR reader) when rustc creates libbluetooth_core_rs.a.

Test: m libbluetooth_core_rs with ToT clang
Change-Id: Ice3152e4265aeba2ff1f11fe4e6f18460c4e7e90