scons: When spawning the linker process, don't involve the shell.

The command line can be too long, causing bash to choke. This means we can't
use any shell syntax like shell variables or redirection when linking, but
that should be easy to avoid.

Change-Id: Ie6c8ecab337cef6bd3c7e403346ced06f46f0993
Reviewed-on: https://gem5-review.googlesource.com/2780
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Steve Reinhardt <stever@gmail.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

src/SConscript

@@ -34,6 +34,7 @@ import imp
 import marshal
 import os
 import re
+import subprocess
 import sys
 import zlib
 
@@ -1194,7 +1195,18 @@ def makeEnv(env, label, objsfx, strip = False, **kwargs):
     if strip:
         progname += '.unstripped'
 
-    targets = new_env.Program(progname, main_objs + static_objs)
+    # When linking the gem5 binary, the command line can be too big for the
+    # shell to handle. Use "subprocess" to spawn processes without passing
+    # through the shell to avoid this problem. That means we also can't use
+    # shell syntax in any of the commands this will run, but that isn't
+    # currently an issue.
+    def spawn_with_subprocess(sh, escape, cmd, args, env):
+        return subprocess.call(args, env=env)
+
+    # Since we're not running through a shell, no escaping is necessary either.
+    targets = new_env.Program(progname, main_objs + static_objs,
+                              SPAWN=spawn_with_subprocess,
+                              ESCAPE=lambda x: x)
 
     if strip:
         if sys.platform == 'sunos5':