build: various fixes

- simplify lua interpreter search
- fix incorrect variable name in BuildLua.cmake
- build PUC Lua with -O2
- silence non-mandatory find_package search for libuv
- simplify Find modules
- Prefer using the explicitly set CI_BUILD over relying on the
  environment variable "CI".

cmake/GenerateVersion.cmake

@@ -7,7 +7,6 @@ execute_process(
   OUTPUT_STRIP_TRAILING_WHITESPACE
   ERROR_QUIET
   RESULT_VARIABLE RES)
-
 if(RES)
   message(STATUS "Using NVIM_VERSION: ${NVIM_VERSION}")
   file(WRITE "${OUTPUT}" "")