[llvm] [Bazel] Export compiler-rt builtins sources (PR #157200)

[Aaron Siddhartha Mondal via llvm-commits]

https://github.com/aaronmondal approved this pull request.

Do keep in mind that it could lead to accidentally "overincluding" files in the future which might lead to bugs that are harder to track down than more obvious "missing file" bugs which can fairly easily be fixed via visual comparison to the CMake sources. Not sure what the better tradeoff is.

https://github.com/llvm/llvm-project/pull/157200