sanitizer_common: initialize sanitizer runtimes lazily from signal interceptors

Currently if a program calls sigaction very early (before non-lazy sanitizer
initialization, in particular if .preinit_array initialization is not enabled),
then sigaction will wrongly fail since the interceptor is not initialized yet.

In all other interceptors we do lazy runtime initialization for this reason,
but we don't do it in the signal interceptors.
Do lazy runtime initialization in signal interceptors as well.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D155188