windows: drop use of msvc helper in build

bootstrap.py

@@ -143,9 +143,7 @@ def run(*args, **kwargs):
 
 Note: to work around Windows file locking, where you can't rebuild an
 in-use binary, to run ninja after making any changes to build ninja itself
-you should run ninja.bootstrap instead.  Your build is also configured to
-use ninja.bootstrap.exe as the MSVC helper; see the --with-ninja flag of
-the --help output of configure.py.""")
+you should run ninja.bootstrap instead.""")
 else:
     print('Building ninja using itself...')
     run([sys.executable, 'configure.py'] + conf_args)

configure.py

@@ -47,9 +47,6 @@
 parser.add_option('--with-python', metavar='EXE',
                   help='use EXE as the Python interpreter',
                   default=os.path.basename(sys.executable))
-parser.add_option('--with-ninja', metavar='NAME',
-                  help="name for ninja binary for -t msvc (MSVC only)",
-                  default="ninja")
 (options, args) = parser.parse_args()
 if args:
     print('ERROR: extra unparsed command-line arguments:', args)
@@ -190,14 +187,11 @@ def shell_escape(str):
 n.newline()
 
 if platform == 'windows':
-    compiler = '$cxx'
-    if options.with_ninja:
-        compiler = ('%s -t msvc -o $out -- $cxx /showIncludes' %
-                    options.with_ninja)
     n.rule('cxx',
-        command='%s $cflags -c $in /Fo$out' % compiler,
+        command='$cxx /showIncludes $cflags -c $in /Fo$out',
         depfile='$out.d',
-        description='CXX $out')
+        description='CXX $out',
+        special='msvc')
 else:
     n.rule('cxx',
         command='$cxx -MMD -MT $out -MF $out.d $cflags -c $in -o $out',