cmake: use the built-in FindThreads module

Summary:
Use CMake's built-in FindThreads module rather than having our own custom
FindPThread.cmake module.

Reviewed By: yfeldblum

Differential Revision: D9212535

fbshipit-source-id: 9a652c510cb310c18547d31bd8215dedd8532a4c

CMake/FindPThread.cmake

-# - Try to find libpthread
-#
-# Once done this will define
-#
-#  LIBPTHREAD_FOUND - system has libpthread
-#  LIBPTHREAD_INCLUDE_DIRS - the libpthread include directory
-#  LIBPTHREAD_LIBRARIES - Link these to use libpthread
-#  LIBPTHREAD_DEFINITIONS - Compiler switches required for using libpthread
-#
-#  Redistribution and use is allowed according to the terms of the New
-#  BSD license.
-#  For details see the accompanying COPYING-CMAKE-SCRIPTS file.
-#
-
-
-if (LIBPTHREAD_LIBRARIES AND LIBPTHREAD_INCLUDE_DIRS)
-  set (LIBPTHREAD_FIND_QUIETLY TRUE)
-endif (LIBPTHREAD_LIBRARIES AND LIBPTHREAD_INCLUDE_DIRS)
-
-find_path (LIBPTHREAD_INCLUDE_DIRS NAMES pthread.h)
-find_library (LIBPTHREAD_LIBRARIES NAMES pthread)
-
-include (FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(LIBPTHREAD DEFAULT_MSG
-  LIBPTHREAD_LIBRARIES LIBPTHREAD_INCLUDE_DIRS)
-
-mark_as_advanced(LIBPTHREAD_INCLUDE_DIRS LIBPTHREAD_LIBRARIES LIBPTHREAD_FOUND)

CMake/folly-deps.cmake

@@ -2,6 +2,13 @@ include(CheckCXXSourceCompiles)
 include(CheckIncludeFileCXX)
 include(CheckFunctionExists)
 
+set(CMAKE_THREAD_PREFER_PTHREAD ON)
+set(THREADS_PREFER_PTHREAD_FLAG ON)
+find_package(Threads REQUIRED)
+set(FOLLY_HAVE_PTHREAD "${CMAKE_USE_PTHREADS_INIT}")
+list(APPEND CMAKE_REQUIRED_LIBRARIES Threads::Threads)
+list(APPEND FOLLY_LINK_LIBRARIES Threads::Threads)
+
 find_package(Boost 1.51.0 MODULE
   COMPONENTS
     context
@@ -74,15 +81,6 @@ list(APPEND CMAKE_REQUIRED_LIBRARIES ${OPENSSL_LIBRARIES})
 list(APPEND CMAKE_REQUIRED_INCLUDES ${OPENSSL_INCLUDE_DIR})
 check_function_exists(ASN1_TIME_diff FOLLY_HAVE_OPENSSL_ASN1_TIME_DIFF)
 
-find_package(PThread MODULE)
-set(FOLLY_HAVE_PTHREAD ${LIBPTHREAD_FOUND})
-if (LIBPTHREAD_FOUND)
-  list(APPEND CMAKE_REQUIRED_LIBRARIES ${LIBPTHREAD_LIBRARIES})
-  list(APPEND CMAKE_REQUIRED_INCLUDES ${LIBPTHREAD_INCLUDE_DIRS})
-  list(APPEND FOLLY_INCLUDE_DIRECTORIES ${LIBPTHREAD_INCLUDE_DIRS})
-  list(APPEND FOLLY_LINK_LIBRARIES ${LIBPTHREAD_LIBRARIES})
-endif()
-
 find_package(ZLIB MODULE)
 set(FOLLY_HAVE_LIBZ ${ZLIB_FOUND})
 if (ZLIB_FOUND)