Reduce the crazy linker's on-disk footprint.
The change to enable libc++ on Android caused a large increase in the size
of libchromium_android_linker.so:
https://codereview.chromium.org/
951983002
Most of this size increase comes from LLVM's __cxa_demangle, but this function
is not required by the crazy linker. Providing a local stub implementation
prevents LLVM's implementation being linked from libc++, and reduces the size
of the crazy linker -- for example from 292kb down to 83kb on ARM.
BUG=502299
Review URL: https://codereview.chromium.org/
1193393008
Cr-Commit-Position: refs/heads/master@{#335659}