Fix OpenACC configuration for LUMI

src/CMakeLists.txt

@@ -84,8 +84,13 @@ check_macro_defined(HAS_OPENACC_MACRO _OPENACC QUIET)
 if (FS_ENABLE_OPENACC)
   # If _OPENACC is defined, assume that the required compiler flags are already
   # provided, e.g. in CMAKE_Fortran_FLAGS:
-  if(NOT HAS_OPENACC_MACRO)
-    find_package(OpenACC REQUIRED)
+  if (NOT HAS_OPENACC_MACRO)
+    # On LUMI, we only have OpenACC_Fortran, but no OpenACC_C
+    find_package(OpenACC QUIET)
+    if (NOT OpenACC_Fortran_FOUND)
+      message(FATAL_ERROR
+        "Could NOT find OpenACC_Fortran.")
+    endif ()
     target_compile_options(fortran-support PRIVATE ${OpenACC_Fortran_OPTIONS})
     # This make sures that unit tests (FortUTF) compiles without the need of
     # passing OpenACC compile option.