[llvm] add bazel build rule for IndexToSPIRV (PR #69743)

[Jeremy Kun via llvm-commits]

j2kun wrote:

Looks like it was reverted in https://github.com/llvm/llvm-project/commit/8b02ceb133341ea6d3e140d0c73ef252fa11415c, but I will leave this open for if/when it is recommitted.

https://github.com/llvm/llvm-project/pull/69743