Reland https://github.com/llvm/llvm-project/pull/133173

Clang spawns a new thread to avoid running out of stack space. This can
make debugging and performance analysis more difficult as how the
threads are connected is difficult to recover.

This patch introduces `runOnNewStack` and applies it in Clang. On
platforms that have good support for it this allocates a new stack and
moves to it using assembly. Doing split stacks like this actually runs
on most platforms, but many debuggers and unwinders reject the large or
backwards stack offsets that occur. Apple platforms and tools are known
to support this, so this only enables it there for now.

…thread to get more stack space (#133173)"

This change breaks the Clang build on Mac AArch64.

This reverts commit d0c973a7a0149db3b71767d4c5a20a31e6a8ed5b. This
reverts commit 429a84f8a4bf559f43f50072747ef49d3e3b2cf1. This reverts
commit 4f64c80d5a23c244f942193e58ecac666c173308.

Clang spawns a new thread to avoid running out of stack space. This can
make debugging and performance analysis more difficult as how the
threads are connected is difficult to recover.

This patch introduces `runOnNewStack` and applies it in Clang. On
platforms that have good support for it this allocates a new stack and
moves to it using assembly. Doing split stacks like this actually runs
on most platforms, but many debuggers and unwinders reject the large or
backwards stack offsets that occur. Apple platforms and tools are known
to support this, so this only enables it there for now.