Merge branch 'partial-fix-for-600' into 'develop'

si_spawn_subprocess: _exit instead of abort if exec fails

See merge request embeddable-common-lisp/ecl!232

src/c/unixsys.d

@@ -529,7 +529,7 @@ si_spawn_subprocess(cl_object command, cl_object argv, cl_object environ,
       }
       /* at this point exec has failed */
       perror("exec");
-      abort();
+      _exit(EXIT_FAILURE);
     }
     close(child_stdin);
     close(child_stdout);