build: FindLibIntl: fix warning about CMP0075 (#10427)

* build: FindLibIntl: fix warning about CMP0075

The common pattern elsewhere to set this only during the check, and here
it was not unset, resulting in a warning later (on Alpine 3.10):

    -- Found Iconv
    -- Looking for pthread.h
    CMake Warning (dev) at /usr/share/cmake/Modules/CheckIncludeFile.cmake:80 (message):
      Policy CMP0075 is not set: Include file check macros honor
      CMAKE_REQUIRED_LIBRARIES.  Run "cmake --help-policy CMP0075" for policy
      details.  Use the cmake_policy command to set the policy and suppress this
      warning.

      CMAKE_REQUIRED_LIBRARIES is set to:

        /usr/lib/libintl.so

      For compatibility with CMake 3.11 and below this check is ignoring it.
    Call Stack (most recent call first):
      /usr/share/cmake/Modules/FindThreads.cmake:105 (CHECK_INCLUDE_FILE)
      CMakeLists.txt:482 (find_package)
    This warning is for project developers.  Use -Wno-dev to suppress it.

    -- Looking for pthread.h - found

* build: remove lists / REMOVE_ITEM around check_c_source_compiles

0 files changed, 0 insertions, 0 deletions