fortran: workaround Absoft linker issue

MTT found that the addition of the MPI_SIZEOF interfaces to mpif.h was
causing a linker error with the Absoft compiler.  Absoft is working on
a fix, but we can workaround the issue for now.  See comment in
Makefile.am in this commit for a lengthy explanation.

Refs trac:4917

This commit was SVN r32797.

The following Trac tickets were found above:
  Ticket 4917 --> https://svn.open-mpi.org/trac/ompi/ticket/4917

ompi/mpi/fortran/mpif-h/Makefile.am

@@ -81,11 +81,35 @@ libmpi_mpifh_la_SOURCES =
 # sizeof_f.f90 is generated based on some results from configure tests.
 CLEANFILES += sizeof_f.f90
 
-nodist_libmpi_mpifh_la_SOURCES =
+# If we're building the MPI_SIZEOF interfaces, generate the source
+# code in sizeof_f.f90 (via a perl script).  Normally, we'd just add
+# sizeof_f.f90 to the libmpi_mpif_la_SOURCES and be done with it.
+# However, since this is the first *actual Fortran* source that we've
+# added to libmpi_mpif_la_SOURCEs, this causes Libtool to use the
+# *Fortran* linker to create the final libmpi_mpif.la library
+# (vs. using the C linker, as it has done for years).  This exposes an
+# unfortunate bug in the Absoft linker: it does not honor the order of
+# -Wl arguments, which basically causes the resulting libmpi_mpif.so
+# to be borked.
+#
+# To get around this, we compile sizeof_f.f90 into its own LT
+# convenience library, and then we LIBADD that convenience library
+# into the main libmpi_mpifh.la.  In this way, we basically trick
+# Libtool into still using the C linker to create libmpi_mpif.la, and
+# our -Wl flags therefore don't get re-ordered.
+#
+# All this being said, we can't rely on Automake/Libtool not figuring
+# out this workaround indefinitely.  So Jeff advised Absoft to fix
+# this bug in Sep 2014.
+noinst_LTLIBRARIES=
 if BUILD_FORTRAN_SIZEOF
-nodist_libmpi_mpifh_la_SOURCES += sizeof_f.f90
+noinst_LTLIBRARIES += libmpi_mpifh_sizeof.la
+libmpi_mpifh_sizeof_la_SOURCES = sizeof_f.f90
+libmpi_mpifh_la_LIBADD += libmpi_mpifh_sizeof.la
 endif
-sizeof_pl=$(top_srcdir)/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
+
+sizeof_pl = $(top_srcdir)/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
+
 sizeof_f.f90: $(top_builddir)/config.status
 sizeof_f.f90: $(sizeof_pl)
 sizeof_f.f90: