Remove Rust cmake Python changes

[jankratochvil]

I did not really understand what they were for, it now builds and testsuites fine for me.
Is this a diff misapplication or do I miss some functionality?

[jankratochvil]

I am closing this as there is https://github.com/rust-lang/llvm-project/tree/rustc/8.0-2019-01-16 although that branch still has some cmakefiles modifications. But the development/maintenance seems to have moved there.

[tromey]

FWIW I recall needing these changes to test the build on Fedora, but indeed it probably isn't truly needed, at least not for Rust. If removing these tweaks works for you, I'm in favor of removing them.

[jankratochvil]

FYI I have tried to remove cmake changes https://people.redhat.com/jkratoch/nocmake.patch but in the branch rustc/8.0-2019-01-16 merged with origin/release/8.x and still "Expected Passes" stayed higher by 4 for those 4 new testcases test_with_dsym_and_python_api() in lldb/packages/Python/lldbsuite/test/lang/rust/ on Fedora 29 x86_64.