Consolidation with CDI-PIO (develop)

Generally, this is !11 (merged) rebased onto the develop branch.

This is the first develop-based version accepted by the Buildbot of ICON: https://buildbot.dkrz.de/grid?branch=m300488/cdi-pio-2-integration

examples/pio/Makefile.am

@@ -10,16 +10,20 @@ if ENABLE_CF_INTERFACE
 check_PROGRAMS += collectData2003
 endif ENABLE_CF_INTERFACE
 
-AM_CPPFLAGS = -I$(top_srcdir)/src $(YAXT_C_INCLUDE)
+AM_CPPFLAGS = -I$(top_srcdir)/src
 if ENABLE_MPI
 AM_CPPFLAGS += -DUSE_MPI
 endif ENABLE_MPI
-AM_CFLAGS = $(MPI_C_INCLUDE)
+AM_CFLAGS = $(YAXT_C_INCLUDE) $(MPI_C_INCLUDE)
 
-AM_FCFLAGS = $(FC_OPTINC)$(top_builddir)/src $(FC_OPTINC)$(top_srcdir)/src $(MPI_FC_INCLUDE)
-if ENABLE_MPI
-AM_FCFLAGS += $(FC_DEFINE)USE_MPI $(YAXT_FC_MOD)
-endif ENABLE_MPI
+AM_FCFLAGS =
+if ENABLE_CF_INTERFACE
+AM_FCFLAGS += $(FC_OPTINC)$(top_builddir)/src $(FC_OPTINC)$(top_srcdir)/src
+endif ENABLE_CF_INTERFACE
+if BUILD_PIO_FC_PROGRAMS
+AM_FCFLAGS += $(FC_DEFINE)USE_MPI
+endif BUILD_PIO_FC_PROGRAMS
+AM_FCFLAGS += $(YAXT_FC_MOD) $(MPI_FC_MOD)
 
 AM_LDFLAGS =
 if ENABLE_ALL_STATIC