Allow the mpirun command to be re-define using the MPIRUN environment variable

PRACE seem to call theirs mpirun_xxx


Former-commit-id: 1d1472e87fd247fa8d6a8124213a545902f2746c

INSTALL.swift

@@ -78,7 +78,8 @@ commands.
 
 MPI: an optional MPI library that fully supports MPI_THREAD_MULTIPLE.  
 Before running configure the "mpirun" command should be available in the
-shell.
+shell. If your command isn't called "mpirun" then define the "MPIRUN"
+environment variable, either in the shell or when running configure.
 
 
 METIS: a build of the METIS library can be optionally used to optimize the

configure.ac

@@ -63,8 +63,12 @@ if test "$enable_mpi" = "yes"; then
 
     # Various MPI implementations require additional libraries when also using
     # threads. Use mpirun (on PATH) as that seems to be only command with
-    # version flag.
-    AC_PATH_PROG([MPIRUN],[mpirun],[notfound])
+    # version flag, allow MPIRUN to override for systems that insist on
+    # a non-standard name (PRACE).
+    : ${MPIRUN='mpirun'}
+    if test "$MPIRUN" = "mpirun"; then
+       AC_PATH_PROG([MPIRUN],[mpirun],[notfound])
+    fi
     if test "$MPIRUN" = "notfound"; then
        AC_MSG_WARN([Cannot find mpirun command on PATH, thread support may not be correct])
        enable_mpi="no"