Don't move llvm.localescape outside the entry block in the GCOV profiling pass

[marco-c]

Summary

This fixes https://bugs.llvm.org/show_bug.cgi?id=34714.

Patch by Marco Castelluccio

[rnk]

lgtm

lib/Transforms/Instrumentation/GCOVProfiling.cpp

550–552

This problematically assumes that all the allocas, dbg.declare, and localescape are all in a contiguous block, but that's a pre-existing issue that you don't need to fix. In practice, clang inserts localescape after allocas.