reset CMAKE_REQUIRED_LIBRARIES before checking system headers

This fixes this CMake warning with CMake 3.12 and newer:

CMake Warning (dev) at /usr/share/cmake/Modules/CheckIncludeFiles.cmake:110 (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/liblzma.so

  For compatibility with CMake 3.11 and below this check is ignoring it.
Call Stack (most recent call first):
  CMakeLists.txt:602 (CHECK_INCLUDE_FILES)
  CMakeLists.txt:609 (LA_CHECK_INCLUDE_FILE)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a5641ade2411be54363acb507696984038066ea4..4d225b3201bbc6b420b04a6036e91fdc39758c23 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -592,6 +592,8 @@ ENDIF(ZSTD_FOUND)
 MARK_AS_ADVANCED(CLEAR ZSTD_INCLUDE_DIR)
 MARK_AS_ADVANCED(CLEAR ZSTD_LIBRARY)
 
+set(CMAKE_REQUIRED_LIBRARIES)
+
 #
 # Check headers
 #