mpi/fortran: Add missing variable marker

 - I'm not sure how this was missed in the cherry-pick from `master`
   but `master` does not have this issue.
 - Related to commit f6f24a4

Signed-off-by: Joshua Hursey <[email protected]>

Author: jjhursey

ompi/mpi/fortran/use-mpi-ignore-tkr/Makefile.am

@@ -53,7 +53,7 @@ endif
 # libmpi_usempi_ignore_tkr.la, so we need to link in the OPAL library
 # directly (pulling it in indirectly via libmpi.la does not work on
 # all platforms).
-libOMPI_LIBMPI_NAME_usempi_ignore_tkr_la_LIBADD = \
+lib@OMPI_LIBMPI_NAME@_usempi_ignore_tkr_la_LIBADD = \
         $(OMPI_MPIEXT_USEMPI_LIBS) \
         $(OMPI_TOP_BUILDDIR)/opal/lib@[email protected]
 lib@OMPI_LIBMPI_NAME@_usempi_ignore_tkr_la_LDFLAGS = \