Autoconf: Detect FMS IO implementation

This patch allows autoconf to detect the version of FMS IO that is
implemented in its library, and select the appropriate "infra" in the
MOM6 source.

The allows for removal of the --with-framework flag, and should prevent
future FMS library/infra mismatches.

.testing/Makefile

@@ -286,7 +286,6 @@ $(BUILD)/unit/Makefile: MOM_ENV += $(COV_FCFLAGS) $(COV_LDFLAGS)
 $(BUILD)/timing/Makefile: MOM_ENV += $(OPT_FCFLAGS) $(MOM_LDFLAGS)
 
 # Configure script flags
-MOM_ACFLAGS := --with-framework=$(FRAMEWORK)
 $(BUILD)/openmp/Makefile: MOM_ACFLAGS += --enable-openmp
 $(BUILD)/coupled/Makefile: MOM_ACFLAGS += --with-driver=FMS_cap
 $(BUILD)/nuopc/Makefile: MOM_ACFLAGS += --with-driver=nuopc_cap

ac/configure.ac

@@ -79,18 +79,6 @@ AS_IF([test "x$with_driver" != "x"],
 # used to configure a header based on a template.
 #AC_CONFIG_HEADERS(["$MEM_LAYOUT/MOM_memory.h"])
 
-# Select the model framework (default: FMS1)
-# NOTE: We can phase this out after the FMS1 I/O has been removed from FMS and
-#   replace with a detection test.  For now, it is a user-defined switch.
-MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS2
-AC_ARG_WITH([framework],
-  AS_HELP_STRING([--with-framework=fms1|fms2], [Select the model framework]))
-AS_CASE(["$with_framework"],
-  [fms1], [MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS1],
-  [fms2], [MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS2],
-  [MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS2]
-)
-
 
 # Explicitly assume free-form Fortran
 AC_LANG(Fortran)
@@ -220,7 +208,6 @@ AX_FC_CHECK_LIB([FMS], [fms_init], [fms_mod],
   ]
 )
 
-
 # Verify that FMS is at least 2019.01.02
 # NOTE: 2019.01.02 introduced two changes:
 #   - diag_axis_init supports an optional domain_position argument
@@ -236,6 +223,14 @@ AC_COMPILE_IFELSE(
   ]
 )
 
+# Determine the FMS IO implementation.
+AX_FC_CHECK_MODULE([fms2_io_mod], [
+  MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS2
+],[
+  MODEL_FRAMEWORK=${srcdir}/config_src/infra/FMS1
+])
+
+
 # Python interpreter test
 
 # Declare the Python interpreter variable