Update entrypoint directly when doing JIT code cache GC.

Otherwise, the Instrumentation::UpdateMethodsCode might access
the declaring class while the GC is concurrently processing
references.

bug:35598395
test: run-libcore-tests.sh --mode=host --variant=X64
Change-Id: I0f059b1823e81672d43cf1f7eed64482f8927232
1 file changed