Fix PIO dep on mpi-serial

PIO needs to depend on mpi-serial in order for the link
order to be correct.

[BFB]

components/cmake/build_model.cmake

@@ -207,11 +207,6 @@ function(build_model COMP_CLASS COMP_NAME)
   # build rules:
   #-------------------------------------------------------------------------------
 
-  if (MPILIB STREQUAL "mpi-serial")
-    set(MPISERIAL "${INSTALL_SHAREDPATH}/lib/libmpi-serial.a")
-    set(MLIBS "${MLIBS} ${MPISERIAL}")
-  endif()
-
   foreach(ITEM IN LISTS SOURCES)
     if (ITEM MATCHES "${CMAKE_BINARY_DIR}/.*") # is generated
       list(APPEND REAL_SOURCES ${ITEM})
@@ -225,7 +220,7 @@ function(build_model COMP_CLASS COMP_NAME)
     add_executable(${TARGET_NAME})
     target_sources(${TARGET_NAME} PRIVATE ${REAL_SOURCES})
 
-    set(ALL_LIBS "${GPTLLIB} ${SLIBS} ${MLIBS}")
+    set(ALL_LIBS "${GPTLLIB} ${SLIBS}")
     separate_arguments(ALL_LIBS_LIST UNIX_COMMAND "${ALL_LIBS}")
 
     foreach(ITEM IN LISTS COMP_CLASSES)

components/cmake/modules/FindPIO.cmake

@@ -28,14 +28,18 @@ find_package(NETCDF REQUIRED)
 # Not all machines/PIO installations use ADIOS but, for now,
 # we can assume that an MPI case with ADIOS2_ROOT set is probably
 # using adios.
-if (NOT MPILIB STREQUAL mpi-serial AND DEFINED ENV{ADIOS2_ROOT})
+if (NOT MPILIB STREQUAL "mpi-serial" AND DEFINED ENV{ADIOS2_ROOT})
   find_package(MPI REQUIRED COMPONENTS C)
   find_package(ADIOS2 REQUIRED COMPONENTS C)
   list(APPEND PIOLIBS adios2::adios2)
 endif()
 
 list(APPEND PIOLIBS netcdf)
 
+if (MPILIB STREQUAL "mpi-serial")
+  list(APPEND PIOLIBS "${INSTALL_SHAREDPATH}/lib/libmpi-serial.a")
+endif()
+
 # Create the interface library, and set target properties
 add_library(spio INTERFACE)
 target_link_libraries(spio INTERFACE ${PIOLIBS})