scons: Make shared library builds work again

Compile gzstream as position independent code
use the PIC version of date for shared libs...oops

ext/gzstream/SConscript

@@ -30,7 +30,7 @@
 
 Import('main')
 
-main.Library('gzstream', [File('gzstream.cc')])
+main.Library('gzstream', [main.SharedObject('gzstream.cc')])
 
 main.Prepend(CPPPATH=Dir('.'))
 main.Append(LIBS=['gzstream'])

src/SConscript

@@ -984,7 +984,7 @@ def makeEnv(label, objsfx, strip = False, **kwargs):
     static_objs.append(static_date)
     
     shared_date = make_obj(date_source, static=False, extra_deps=shared_objs)
-    shared_objs.append(static_date)
+    shared_objs.append(shared_date)
 
     # First make a library of everything but main() so other programs can
     # link against m5.