cmake: compiler feature checks before flags

Author: scivision

cmake/compilers.cmake

@@ -1,5 +1,22 @@
 set(CMAKE_CONFIGURATION_TYPES "Release;RelWithDebInfo;Debug" CACHE STRING "Build type selections" FORCE)
 
+
+include(CheckCSourceCompiles)
+include(CheckCSourceRuns)
+include(CheckFortranSourceCompiles)
+
+include(${CMAKE_CURRENT_LIST_DIR}/f08block.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f08contig.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f18errorstop.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f18random.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f18assumed_rank.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f08kind.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f18prop.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f08command.cmake)
+include(${CMAKE_CURRENT_LIST_DIR}/f03ieee.cmake)
+
+# compiler feature checks BEFORE setting flags to avoid intermittant failures in general
+
 if(CMAKE_Fortran_COMPILER_ID STREQUAL Intel)
   if(WIN32)
     add_compile_options(/arch:native)
@@ -29,17 +46,3 @@ elseif(CMAKE_Fortran_COMPILER_ID STREQUAL NAG)
   # https://www.nag.co.uk/nagware/np/r70_doc/manual/compiler_2_4.html#OPTIONS
   string(APPEND CMAKE_Fortran_FLAGS " -f2018 -C -colour -gline -nan -info -u")
 endif()
-
-include(CheckCSourceCompiles)
-include(CheckCSourceRuns)
-include(CheckFortranSourceCompiles)
-
-include(${CMAKE_CURRENT_LIST_DIR}/f08block.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f08contig.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f18errorstop.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f18random.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f18assumed_rank.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f08kind.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f18prop.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f08command.cmake)
-include(${CMAKE_CURRENT_LIST_DIR}/f03ieee.cmake)