Find* (and some other): use ${CMAKE_CURRENT_LIST_DIR} in include()

This solves a lots of warnings, e.g. in the FindModulesExecuteAll test. If the
installed version on the system is rather old this may even lead to bugs, e.g.
https://bugs.gentoo.org/show_bug.cgi?id=436540

Modules/FindOpenMP.cmake

@@ -95,7 +95,7 @@ if(CMAKE_C_COMPILER_LOADED)
     unset(OpenMP_C_FLAG_CANDIDATES)
   else()
     _OPENMP_FLAG_CANDIDATES("C")
-    include(CheckCSourceCompiles)
+    include(${CMAKE_CURRENT_LIST_DIR}/CheckCSourceCompiles.cmake)
   endif()
 
   foreach(FLAG ${OpenMP_C_FLAG_CANDIDATES})
@@ -126,7 +126,7 @@ if(CMAKE_CXX_COMPILER_LOADED)
     unset(OpenMP_CXX_FLAG_CANDIDATES)
   else()
     _OPENMP_FLAG_CANDIDATES("CXX")
-    include(CheckCXXSourceCompiles)
+    include(${CMAKE_CURRENT_LIST_DIR}/CheckCXXSourceCompiles.cmake)
 
     # use the same source for CXX as C for now
     set(OpenMP_CXX_TEST_SOURCE ${OpenMP_C_TEST_SOURCE})