Revert "[llvm] cmake config groundwork to have ZSTD in LLVM"

This reverts commit f07caf20b9d35e45501c9d5d903fa182b3bdb95a which seems to break upstream https://lab.llvm.org/buildbot/#/builders/109/builds/42253.

GitOrigin-RevId: 474c873148b1441f1dd7a2b269441a1b20e30aa2