[cmake] Add missing CMakePushCheckState include to FindLibEdit.cmake

[mgorny]

Summary

Add the missing include to fix an error when cmake_push_check_state()
is called and incidentally the CMakePushCheckState module is not loaded
by any other check running prior to FindLibEdit.cmake:

CMake Error at /var/no-tmpfs/portage/dev-util/lldb-15.0.4/work/cmake/Modules/FindLibEdit.cmake:24 (cmake_push_check_state):
  Unknown CMake command "cmake_push_check_state".
Call Stack (most recent call first):
  cmake/modules/LLDBConfig.cmake:52 (find_package)
  cmake/modules/LLDBConfig.cmake:59 (add_optional_dependency)
  CMakeLists.txt:28 (include)

Gentoo Bug: https://bugs.gentoo.org/880065

[upsj]

LGTM! My bad, thanks for fixing this

[mgorny]

Thanks!

cmake/Modules/FindLibEdit.cmake

 find_package(PkgConfig QUIET)
 pkg_check_modules(PC_LIBEDIT QUIET libedit)
 
 find_path(LibEdit_INCLUDE_DIRS NAMES histedit.h HINTS ${PC_LIBEDIT_INCLUDE_DIRS})
 find_library(LibEdit_LIBRARIES NAMES edit HINTS ${PC_LIBEDIT_LIBRARY_DIRS})
 
 include(CheckIncludeFile)
 if(LibEdit_INCLUDE_DIRS AND EXISTS "${LibEdit_INCLUDE_DIRS}/histedit.h")
+  include(CMakePushCheckState)
   cmake_push_check_state()
   list(APPEND CMAKE_REQUIRED_INCLUDES ${LibEdit_INCLUDE_DIRS})
   list(APPEND CMAKE_REQUIRED_LIBRARIES ${LibEdit_LIBRARIES})
   check_include_file(histedit.h HAVE_HISTEDIT_H)
   cmake_pop_check_state()
   if (HAVE_HISTEDIT_H)
     file(STRINGS "${LibEdit_INCLUDE_DIRS}/histedit.h"
           libedit_major_version_str