autogen/generator.py: Make the output reproducible (#48)

Whilst working on the Reproducible Builds effort [0], we noticed
that cypari2 could not be built reproducibly as it embeds the
absolute build path in the generated .pxd files.

 [0] https://reproducible-builds.org/

Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>

Author: lamby

autogen/generator.py

@@ -30,7 +30,7 @@
     This class is not meant to be used directly, use the derived class
     :class:`Gen` instead.
     """
-'''.format(__file__)
+'''.format(os.path.relpath(__file__, os.getcwd()))
 
 instance_banner = '''# This file is auto-generated by {}
 
@@ -41,7 +41,7 @@
     You must never use this class directly (in fact, Python may crash
     if you do), use the derived class :class:`Pari` instead.
     """
-'''.format(__file__)
+'''.format(os.path.relpath(__file__, os.getcwd()))
 
 decl_banner='''# This file is auto-generated by {}