Replace FOLLY_HAVE_FEATURES_H with __has_include

Summary:
[Folly] Replace `FOLLY_HAVE_FEATURES_H` with `__has_include`.

Now that folly only targets which support `__has_include`.

Reviewed By: simpkins

Differential Revision: D9281991

fbshipit-source-id: 2e263681df5a980220fc133e8ac0495f229f6084

CMake/FollyConfigChecks.cmake

@@ -6,7 +6,6 @@ include(CheckSymbolExists)
 include(CheckTypeSize)
 include(CheckCXXCompilerFlag)
 
-CHECK_INCLUDE_FILE_CXX(features.h FOLLY_HAVE_FEATURES_H)
 CHECK_INCLUDE_FILE_CXX(jemalloc/jemalloc.h FOLLY_USE_JEMALLOC)
 
 if(NOT CMAKE_SYSTEM_NAME STREQUAL "Windows")

CMake/folly-config.h.cmake

@@ -35,10 +35,9 @@
 
 #cmakedefine FOLLY_HAVE_LIBGLOG 1
 
-#cmakedefine FOLLY_HAVE_FEATURES_H 1
 #cmakedefine FOLLY_USE_JEMALLOC 1
 
-#if FOLLY_HAVE_FEATURES_H
+#if __has_include(<features.h>)
 #include <features.h>
 #endif
 

folly/io/async/EventFDWrapper.h

@@ -25,7 +25,7 @@
 #include <folly/folly-config.h>
 #endif
 
-#ifdef FOLLY_HAVE_FEATURES_H
+#if __has_include(<features.h>)
 #include <features.h>
 #endif
 

folly/portability/Config.h

@@ -24,7 +24,7 @@
 #include FOLLY_PLATFORM_CONFIG
 #endif
 
-#if FOLLY_HAVE_FEATURES_H
+#if __has_include(<features.h>)
 #include <features.h> // @manual
 #endif