require version 1.3 for building ninja itself

This catches the case where you use an older version on Ninja
to build a newer version of the Ninja code.
bootstrap.py always should work regardless.

diff --git a/configure.py b/configure.py
index 1284deb..7c90e66 100755 (executable)
--- a/configure.py
+++ b/configure.py
@@ -65,6 +65,9 @@ n.comment('This file is used to build ninja itself.')
 n.comment('It is generated by ' + os.path.basename(__file__) + '.')
 n.newline()
 
+n.variable('ninja_required_version', '1.3')
+n.newline()
+
 n.comment('The arguments passed to configure.py, for rerunning it.')
 n.variable('configure_args', ' '.join(sys.argv[1:]))
 env_keys = set(['CXX', 'AR', 'CFLAGS', 'LDFLAGS'])