Merge pull request #2541 from neundorf/AvoidRebuildsWhenEnablingExamples

avoid recompiles when enabling/disabling examples

CMakeLists.txt

@@ -604,9 +604,7 @@ hpx_option(HPX_WITH_EXAMPLES_OPENMP BOOL
   CATEGORY "Tools" ADVANCED)
 if(HPX_WITH_EXAMPLES_OPENMP)
   find_package(OpenMP)
-  if(OPENMP_FOUND)
-    hpx_add_config_define(HPX_HAVE_EXAMPLES_OPENMP)
-  else()
+  if(NOT OPENMP_FOUND)
     set(HPX_WITH_EXAMPLES_OPENMP OFF)
   endif()
 endif()
@@ -615,9 +613,7 @@ hpx_option(HPX_WITH_EXAMPLES_TBB BOOL
   CATEGORY "Tools" ADVANCED)
 if(HPX_WITH_EXAMPLES_TBB)
   find_package(TBB)
-  if(TBB_FOUND)
-    hpx_add_config_define(HPX_HAVE_EXAMPLES_TBB)
-  else()
+  if(NOT TBB_FOUND)
     set(HPX_WITH_EXAMPLES_TBB OFF)
   endif()
 endif()
@@ -626,9 +622,7 @@ hpx_option(HPX_WITH_EXAMPLES_QTHREADS BOOL
   CATEGORY "Tools" ADVANCED)
 if(HPX_WITH_EXAMPLES_QTHREADS)
   find_package(QThreads)
-  if(QTHREADS_FOUND)
-    hpx_add_config_define(HPX_HAVE_EXAMPLES_QTHREADS)
-  else()
+  if(NOT QTHREADS_FOUND)
     set(HPX_WITH_EXAMPLES_QTHREADS OFF)
   endif()
 endif()
@@ -637,9 +631,7 @@ hpx_option(HPX_WITH_EXAMPLES_HDF5 BOOL
   CATEGORY "Tools" ADVANCED)
 if(HPX_WITH_EXAMPLES_HDF5)
   find_package(HDF5 COMPONENTS CXX)
-  if(HDF5_FOUND)
-    hpx_add_config_define(HPX_HAVE_EXAMPLES_HDF5)
-  else()
+  if(NOT HDF5_FOUND)
     set(HPX_WITH_EXAMPLES_HDF5 OFF)
   endif()
 endif()
@@ -651,9 +643,7 @@ if(NOT "${HPX_PLATFORM_UC}" STREQUAL "BLUEGENEQ")
     CATEGORY "Tools" ADVANCED)
   if(HPX_WITH_EXAMPLES_QT4)
     find_package(Qt4)
-    if(QT4_FOUND)
-      hpx_add_config_define(HPX_HAVE_EXAMPLES_QT4)
-    else()
+    if(NOT QT4_FOUND)
       set(HPX_WITH_EXAMPLES_QT4 OFF)
     endif()
   endif()