Replace snprintf calls in linker.

When enabling debug malloc, the snprintf calls in the linker fails to
update the buffer.

The problem is that snprintf makes a call to pthread_getspecific that
returns a valid pointer, but the data it points to is zero. This should
never happen and causes the snprintf to stop and do nothing.

Temporarily replace snprintf with a different implementation to work
around this issue.

Bug: 16874447
Bug: 17302493

(cherry pick from commit 172955a4)

Change-Id: Idca9d417978403d61debfd0434aaa82fd770f33b