[llvm] Reenable JumpTableToSwitch pass by default (PR #83229)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Even with the lower threshold this is still taking (so far) over an hour and a half to compile one of the files in flang.

This is the full command in case you spot anything that would make a big difference between our configurations:
```
david.s+  875475  875466 97 378333 1407632 76 09:32 pts/5  01:33:17 /home/david.spickett/build-llvm-aarch64/bin/clang++ -DFLANG_INCLUDE_TESTS=1 -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/david.spickett/build-llvm-stage-2/tools/flang/lib/Semantics -I/home/david.spickett/llvm-project/flang/lib/Semantics -I/home/david.spickett/llvm-project/flang/include -I/home/david.spickett/build-llvm-stage-2/tools/flang/include -I/home/david.spickett/build-llvm-stage-2/include -I/home/david.spickett/llvm-project/llvm/include -isystem /home/david.spickett/llvm-project/llvm/../mlir/include -isystem /home/david.spickett/build-llvm-stage-2/tools/mlir/include -isystem /home/david.spickett/build-llvm-stage-2/tools/clang/include -isystem /home/david.spickett/llvm-project/llvm/../clang/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Wno-deprecated-copy -Wno-string-conversion -Wno-ctad-maybe-unsupported -Wno-unused-command-line-argument -Wstring-conversion -Wcovered-switch-default -Wno-nested-anon-types -O3 -DNDEBUG -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT tools/flang/lib/Semantics/CMakeFiles/obj.FortranSemantics.dir/check-do-forall.cpp.o -MF tools/flang/lib/Semantics/CMakeFiles/obj.FortranSemantics.dir/check-do-forall.cpp.o.d -o tools/flang/lib/Semantics/CMakeFiles/obj.FortranSemantics.dir/check-do-forall.cpp.o -c /home/david.spickett/llvm-project/flang/lib/Semantics/check-do-forall.cpp
```

Stage 1 clang is release with asserts, to match the buildbot https://lab.llvm.org/buildbot/#/builders/179/builds/9480. Host is Linux on AArch64, the processor is an Ampere Altra (Neoverse N1) and the machine isn't loaded, so it's got all the cpu time it wants.

(just including all this info for context)

I will try lowering the threshold more to see if there's a sudden change in the build times.

https://github.com/llvm/llvm-project/pull/83229