Switch to clang-r353983b.

This is the current toolchain version being used in
build/soong/cc/config/global.go, so it should be used here as well.
Ideally, this python file would be updated to pick up the value directly
from the build configuration.

Test: N/A
Change-Id: I1c615a0d0c6dc4dedd82d1ced0381bab273f9e61