Scons: fix the Win32Spawn

Windows(tm) CreateProcess does not use the env passed to it to find the
executables. So we have to modify our own PATH to make Popen work. Also,
detect the cmd build-in commands and execute it directly.

Tested on MDK toolchain on RB4088 and the MSVS toolchain on simulator
BSP.

tools/building.py

@@ -12,24 +12,43 @@ Env = None
 
 class Win32Spawn:
     def spawn(self, sh, escape, cmd, args, env):
+        # deal with the cmd build-in commands which cannot be used in
+        # subprocess.Popen
+        if cmd == 'del':
+            for f in args[1:]:
+                try:
+                    os.remove(f)
+                except Exception as e:
+                    print 'Error removing file: %s' % e
+                    return -1
+            return 0
+
         import subprocess
 
         newargs = string.join(args[1:], ' ')
         cmdline = cmd + " " + newargs
         startupinfo = subprocess.STARTUPINFO()
+        startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+
+        # Make sure the env is constructed by strings
+        _e = {k: str(v) for k, v in env.items()}
 
-        proc = subprocess.Popen(cmdline, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE, startupinfo=startupinfo, shell = False)
-        data, err = proc.communicate()
-        rv = proc.wait()
-        if data:
-            print data
-        if err:
-            print err
+        # Windows(tm) CreateProcess does not use the env passed to it to find
+        # the executables. So we have to modify our own PATH to make Popen
+        # work.
+        old_path = os.environ['PATH']
+        os.environ['PATH'] = _e['PATH']
+
+        try:
+            proc = subprocess.Popen(cmdline, env=_e,
+                    startupinfo=startupinfo, shell=False)
+        except Exception as e:
+            print 'Error in Popen: %s' % e
+            return -1
+        finally:
+            os.environ['PATH'] = old_path
 
-        if rv:
-            return rv
-        return 0
+        return proc.wait()
 
 def PrepareBuilding(env, root_directory, has_libcpu=False, remove_components = []):
     import SCons.cpp
@@ -59,11 +78,11 @@ def PrepareBuilding(env, root_directory, has_libcpu=False, remove_components = [
         env['LIBDIRPREFIX'] = '--userlibpath '
 
     # patch for win32 spawn
-    if env['PLATFORM'] == 'win32' and rtconfig.PLATFORM == 'gcc':
+    if env['PLATFORM'] == 'win32':
         win32_spawn = Win32Spawn()
         win32_spawn.env = env
         env['SPAWN'] = win32_spawn.spawn
-    
+
     if env['PLATFORM'] == 'win32':
         os.environ['PATH'] = rtconfig.EXEC_PATH + ";" + os.environ['PATH']
     else: