properly search for the new isa simulator (spike)

aclocal.m4

@@ -120,7 +120,7 @@ AC_DEFUN([MCPPBS_PROG_RUN],
 [
   AS_IF([ test "${build}" != "${host}" ],
   [
-    AC_CHECK_TOOLS([RUN],[isa-run run],[no])
+    AC_CHECK_TOOLS([RUN],[spike],[no])
     AS_IF([ test ${RUN} = "no" ],
     [
       AC_MSG_ERROR([Cannot find simulator for target ${target_alias}])

configure

@@ -3447,7 +3447,7 @@ fi
   if  test "${build}" != "${host}" ; then :
 
     if test -n "$ac_tool_prefix"; then
-  for ac_prog in isa-run run
+  for ac_prog in spike
   do
     # Extract the first word of "$ac_tool_prefix$ac_prog", so it can be a program name with args.
 set dummy $ac_tool_prefix$ac_prog; ac_word=$2
@@ -3491,7 +3491,7 @@ fi
 fi
 if test -z "$RUN"; then
   ac_ct_RUN=$RUN
-  for ac_prog in isa-run run
+  for ac_prog in spike
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2