Temporarily loosen this test so I can cherry-pick an llvm fix that
throws away dead profile name variables. I will tighten it up again when
the llvm change lands.
While invoking the instrprof_increment intrinsic, we used to pass the
profile name variable by using a GEP instruction to get to the string
constant. That prevented llvm from uniquing the names. Use a constexpr
GEP to fix the issue.
Fix a crash in emitBuiltinCall() which occurs because we drop function
linkage information when creating SILCoverageMaps.
This re-applies 45c7e4e86 with the MachO-specific checks in the test
case removed.