Configure/compilation fails when --without-mpi is set and gfortran is not installed

[gllort]

Steps to reproduce:

1. Uninstall gfortran:

apt remove gfortran

2. Configure without MPI support:

./configure --without-mpi --without-unwind --without-binutils --without-papi --without-dyninst --disable-openmp-intel --prefix=$PWD/install

This configure fails because AC_FC_WRAPPERS will not work if there's no FC set (configure.ac, line 126):

AM_CONDITIONAL(HAVE_FC, test "$FC" != "")
if test "${IS_SPARC64_MACHINE}" != "yes"; then
        AC_FC_WRAPPERS
fi

The call to AC_FC_WRAPPERS could be protected like this:

AM_CONDITIONAL(HAVE_FC, test "$FC" != "")
if test "${IS_SPARC64_MACHINE}" != "yes" -a test "$FC" != ""; then
        AC_FC_WRAPPERS
fi

3. make

...
make[5]: Entering directory '/home/gllort/Work/extrae.git/wt/test-no-fortran-compiler/src/tracer/interfaces/API'
  CC       libiface_api_la-misc_interface.lo
In file included from ../../../../src/tracer/wrappers/API/wrapper.h:74,
                 from misc_interface.c:44:
../../../../src/tracer/defines.h:57:4: error: #error "Error! Not defined FC_FUNC, how do we deal with Fortran symbols?"
   57 | #  error "Error! Not defined FC_FUNC, how do we deal with Fortran symbols?"
      |    ^~~~~