scons: Delete unnecessary imports from SConstruct.

Also get rid of the joinpath and splitpath aliases for os.path.join and
os.path.split. The aliases are only slightly shorter, and obscure these
extremely common python methods.

Change-Id: I0784e2d8dbaacb0690a59e9fa8c8258c1df0e6c3
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40874
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

SConstruct

@@ -77,15 +77,13 @@
 
 # Global Python includes
 import atexit
-import collections
-import itertools
 import os
 import sys
 
 from os import mkdir, environ
-from os.path import abspath, basename, dirname, expanduser, normpath
-from os.path import exists,  isdir, isfile
-from os.path import join as joinpath, split as splitpath
+from os.path import abspath, dirname, expanduser
+from os.path import isdir, isfile
+from os.path import join, split
 from re import match
 
 # SCons includes
@@ -165,7 +163,7 @@ def rfind(l, elt, offs = -1):
 # paths made absolute and ~-expanded.  Paths will be interpreted
 # relative to the launch directory unless a different root is provided
 def makePathListAbsolute(path_list, root=GetLaunchDir()):
-    return [abspath(joinpath(root, expanduser(str(p))))
+    return [abspath(os.path.join(root, expanduser(str(p))))
             for p in path_list]
 
 # Each target must have 'build' in the interior of the path; the
@@ -203,7 +201,7 @@ main['BUILDROOT'] = build_root
 
 Export('main')
 
-main.SConsignFile(joinpath(build_root, "sconsign"))
+main.SConsignFile(os.path.join(build_root, "sconsign"))
 
 # Default duplicate option is to use hard links, but this messes up
 # when you use emacs to edit a file in the target dir, as emacs moves
@@ -216,7 +214,7 @@ main.SetOption('duplicate', 'soft-copy')
 # tree (not specific to a particular build like X86)
 #
 
-global_vars_file = joinpath(build_root, 'variables.global')
+global_vars_file = os.path.join(build_root, 'variables.global')
 
 global_vars = Variables(global_vars_file, args=ARGUMENTS)
 
@@ -603,8 +601,8 @@ for bdir in [ base_dir ] + extras_dir_list:
     for root, dirs, files in os.walk(bdir):
         if 'SConsopts' in files:
             if GetOption('verbose'):
-                print("Reading", joinpath(root, 'SConsopts'))
-            SConscript(joinpath(root, 'SConsopts'))
+                print("Reading", os.path.join(root, 'SConsopts'))
+            SConscript(os.path.join(root, 'SConsopts'))
 
 for cb in after_sconsopts_callbacks:
     cb()
@@ -687,10 +685,10 @@ for root, dirs, files in os.walk(ext_dir):
     if 'SConscript' in files:
         build_dir = os.path.relpath(root, ext_dir)
         ext_build_dirs.append(build_dir)
-        main.SConscript(joinpath(root, 'SConscript'),
-                        variant_dir=joinpath(build_root, build_dir))
+        main.SConscript(os.path.join(root, 'SConscript'),
+                        variant_dir=os.path.join(build_root, build_dir))
 
-gdb_xml_dir = joinpath(ext_dir, 'gdb-xml')
+gdb_xml_dir = os.path.join(ext_dir, 'gdb-xml')
 Export('gdb_xml_dir')
 
 ###################################################
@@ -742,14 +740,14 @@ for variant_path in variant_paths:
 
     # variant_dir is the tail component of build path, and is used to
     # determine the build parameters (e.g., 'X86')
-    (build_root, variant_dir) = splitpath(variant_path)
+    (build_root, variant_dir) = os.path.split(variant_path)
 
     # Set env variables according to the build directory config.
     sticky_vars.files = []
     # Variables for $BUILD_ROOT/$VARIANT_DIR are stored in
     # $BUILD_ROOT/variables/$VARIANT_DIR so you can nuke
     # $BUILD_ROOT/$VARIANT_DIR without losing your variables settings.
-    current_vars_file = joinpath(build_root, 'variables', variant_dir)
+    current_vars_file = os.path.join(build_root, 'variables', variant_dir)
     if isfile(current_vars_file):
         sticky_vars.files.append(current_vars_file)
         if not GetOption('silent'):
@@ -771,10 +769,12 @@ for variant_path in variant_paths:
         default = GetOption('default')
         opts_dir = Dir('#build_opts').abspath
         if default:
-            default_vars_files = [joinpath(build_root, 'variables', default),
-                                  joinpath(opts_dir, default)]
+            default_vars_files = [
+                    os.path.join(build_root, 'variables', default),
+                    os.path.join(opts_dir, default)
+                ]
         else:
-            default_vars_files = [joinpath(opts_dir, variant_dir)]
+            default_vars_files = [os.path.join(opts_dir, variant_dir)]
         existing_files = list(filter(isfile, default_vars_files))
         if existing_files:
             default_vars_file = existing_files[0]