[llvm] Enable JumpTableToSwitch pass by default (PR #82546)

[David Spickett via llvm-commits]

DavidSpickett wrote:

I've reverted this due to a timeout (which is set to 20 minutes) in the second stage of our AArch64 builders that include Flang.

https://lab.llvm.org/buildbot/#/builders/179/builds/9442

Reproducer: [FlangRepro.zip](https://github.com/llvm/llvm-project/files/14405452/FlangRepro.zip)

```
$ time /home/david.spickett/build-llvm-aarch64/bin/clang++   -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -fdiagnostics-color   -ffunction-sections -fdata-sections   -Wno-unused-command-line-argument   -Wno-gnu-line-marker -Wno-unused-value   -O3 -DNDEBUG -fno-exceptions   -funwind-tables -fno-rtti -UNDEBUG -std=c++17   -o /dev/null   -c /home/david.spickett/FlangRepro.cpp
```

Prior to this patch, an asserts enabled clang takes around 2 minutes. After the patch, I've seen it taking upwards of 20 minutes (could be even more, didn't stick around to find out).

Looking at the remaining processes at the end of the build, it's all flang stuff:  [files.log](https://github.com/llvm/llvm-project/files/14405474/files.log)

They probably all include some header or use the same pattern that causes this.



https://github.com/llvm/llvm-project/pull/82546