[PATCH] cmake: fix sync_file_range detection

[Vladimir Davydov <vdavydov.dev@gmail.com>]

sync_file_range is declared only if _GNU_SOURCE macro is defined.
Also, in order to be used in a source file, HAVE_SYNC_FILE_RANGE
must be present in config.h.cmake.

Fixes commit caae99e5eaa0 ("Refactor xlog writer").
---
https://github.com/tarantool/tarantool/commits/dv/cmake-fix-gnu-symbol-detection

 CMakeLists.txt            | 2 ++
 src/trivia/config.h.cmake | 1 +
 2 files changed, 3 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bf68d187..b26d2abf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -69,6 +69,8 @@ include(cmake/profile.cmake)
 include(cmake/module.cmake)
 include(cmake/thread.cmake)
 
+list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+
 check_symbol_exists(MAP_ANON sys/mman.h HAVE_MAP_ANON)
 check_symbol_exists(MAP_ANONYMOUS sys/mman.h HAVE_MAP_ANONYMOUS)
 check_include_file(sys/time.h HAVE_SYS_TIME_H)
diff --git a/src/trivia/config.h.cmake b/src/trivia/config.h.cmake
index 66ddba99..8894b436 100644
--- a/src/trivia/config.h.cmake
+++ b/src/trivia/config.h.cmake
@@ -167,6 +167,7 @@
 #cmakedefine HAVE_SCHED_YIELD 1
 #cmakedefine HAVE_POSIX_FADVISE 1
 #cmakedefine HAVE_MREMAP 1
+#cmakedefine HAVE_SYNC_FILE_RANGE 1
 
 #cmakedefine HAVE_PRCTL_H 1
 
-- 
2.11.0