SanitizerCoverage: Use `createSanitizerCtor` to create ctor and call init

Second attempt; instead of using a named local variable, passing
arguments directly to `createSanitizerCtorAndInitFunctions` worked
on Windows.

Reviewers: kcc, samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8780

llvm-svn: 236951