mark AIBinder_Class_setHandleShellCommand as weak.

This symbol is not present on Q builds. This breaks installing
mainline modules on Q builds.

Bug: 149077229

Test: TARGET_BUILD_APPS=com.android.resolv vendor/google/build/build_unbundled_mainline_module.sh com.android.resolv && adb install --staged --enable-rollback out/dist/mainline_modules_arm64/com.android.resolv.apex && adb reboot
Change-Id: I4fae98f2ad3051d758707658ec489f0d855cd4b6