Revert "Use `GNUInstallDirs` to support custom installation dirs. -- LLVM"

This reverts commit 6fd2db04d0f22ea22c5317d98ce2126aa64b6a73 since it
broke GreenDragon LLDB-Incremental bot:

https://green.lab.llvm.org/green/job/lldb-cmake/37560/console

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
GitOrigin-RevId: 797b50d4be873b4662983413a06806fca544c276
1 file changed