Do not use -isystem to add headers, as they break GCC 6's header wrapping.
See also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129

diff --git a/client/CMakeLists.txt b/client/CMakeLists.txt
index dbf1c48..e5d7347 100644
--- a/client/CMakeLists.txt
+++ b/client/CMakeLists.txt
@@ -52,7 +52,7 @@ IF(NOT WITHOUT_SERVER)
     upgrade/program.cc
   )
 ADD_COMPILE_FLAGS(
-  upgrade/program.cc COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  upgrade/program.cc COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
 )
 TARGET_LINK_LIBRARIES(mysql_upgrade mysqlclient client_base mysqlcheck_core)
 ADD_DEPENDENCIES(mysql_upgrade GenFixPrivs GenSysSchema)
diff --git a/client/base/CMakeLists.txt b/client/base/CMakeLists.txt
index b206de7..91cce4c 100644
--- a/client/base/CMakeLists.txt
+++ b/client/base/CMakeLists.txt
@@ -49,7 +49,7 @@ ADD_COMPILE_FLAGS(
   mutex.cc
   mysql_query_runner.cc
   show_variable_query_extractor.cc
-  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
 )
 
 TARGET_LINK_LIBRARIES(client_base mysqlclient)
diff --git a/client/dump/CMakeLists.txt b/client/dump/CMakeLists.txt
index fdbb631..bae2ce7 100644
--- a/client/dump/CMakeLists.txt
+++ b/client/dump/CMakeLists.txt
@@ -50,7 +50,7 @@ IF(USING_LOCAL_BOOST)
 
   ADD_COMPILE_FLAGS(
     ${BOOST_LIB_SOURCES}
-    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
     )
 
   IF(HAVE_clock_gettime_IN_rt)
@@ -145,7 +145,7 @@ TARGET_LINK_LIBRARIES(mysqlpump_lib
 
 ADD_COMPILE_FLAGS(
   ${MYSQLPUMP_LIB_SOURCES}
-  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
   )
 
 # Files that use Boost sources that trigger compilation warnings
@@ -179,7 +179,7 @@ ADD_COMPILE_FLAGS(
 )
 MYSQL_ADD_EXECUTABLE(mysqlpump  program.cc)
 ADD_COMPILE_FLAGS(
-  program.cc COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  program.cc COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
 )
 
 TARGET_LINK_LIBRARIES(mysqlpump mysqlpump_lib ${LOCAL_BOOST_LIB})
diff --git a/libmysqld/CMakeLists.txt b/libmysqld/CMakeLists.txt
index 44c1d26..dac03d9 100644
--- a/libmysqld/CMakeLists.txt
+++ b/libmysqld/CMakeLists.txt
@@ -123,7 +123,7 @@ ADD_COMPILE_FLAGS(
   ../sql/item_geofunc_setops.cc
   ../sql/item_json_func.cc
   ../sql/spatial.cc
-  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
 )
 
 ADD_COMPILE_FLAGS(
diff --git a/sql/CMakeLists.txt b/sql/CMakeLists.txt
index 1d1231f..9a35fa8 100644
--- a/sql/CMakeLists.txt
+++ b/sql/CMakeLists.txt
@@ -312,7 +312,7 @@ ADD_COMPILE_FLAGS(
   item_geofunc_setops.cc
   item_json_func.cc
   spatial.cc
-  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+  COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
 )
 
 ADD_COMPILE_FLAGS(
diff --git a/unittest/gunit/CMakeLists.txt b/unittest/gunit/CMakeLists.txt
index f0123b8..f2169f9 100644
--- a/unittest/gunit/CMakeLists.txt
+++ b/unittest/gunit/CMakeLists.txt
@@ -385,7 +385,7 @@ IF (MERGE_UNITTESTS)
   ENDIF()
   ADD_COMPILE_FLAGS(
     ${MERGE_SMALL_TESTS}
-    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
   )
   # Fixes "C1128: number of sections exceeded object file format limit" in MSVC
   IF(WIN32)
@@ -467,11 +467,11 @@ ENDIF(MERGE_UNITTESTS)
   ENDIF()
   ADD_COMPILE_FLAGS(
     bounded_queue-t.cc
-    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
   )
   ADD_COMPILE_FLAGS(
     pump_object_filter-t.cc
-    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -isystem ${BOOST_INCLUDE_DIR}
+    COMPILE_FLAGS -I${BOOST_PATCHES_DIR} -I${BOOST_INCLUDE_DIR}
   )
 
   FOREACH(test ${SERVER_TESTS})