[WebAssembly] Opt out of enableTiedFastRegAlloc (#229814)
Commit 69fa41f715fddf7028c0399e4a54e89911d095c9 enabled
EnableTiedFastRegAlloc by default in TargetMachine.cpp, which skips
TwoAddressInstructionPass at -O0 under the expectation that RegAllocFast
will lower tied operands.
However, WebAssembly does not use a register allocator, so skipping
TwoAddressInstructionPass causes tied operands (such
as in inline assembly using '+r' constraints) to never be lowered,
leaving the tied output registers uninitialized.
Opt out of enableTiedFastRegAlloc in WebAssemblyTargetMachine so that
TwoAddressInstructionPass continues to run at -O0.
