[release/9.0] [mono] Revert "don't define HAS_CUSTOM_BLOCKS on mono (#106764)" #107675
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Backport of #107558 to release/9.0
/cc @matouskozak
Customer Impact
The #106801 caused significant improvements for MonoJIT but introduced unexpected regressions for MonoAOT/MonoInterpreter described at #107308 (comment). We decided that the safest approach for .NET 9 is to keep MonoJIT regressed and do not introduce new regressions to MonoAOT and MonoInterpreter.
Regression
Found using Performance measurements on dotnet/runtime main.
Testing
Revert of #106801, we expect to get to the state before the original commit.
Risk
Low: this is a revert of previous backport #106801.