./buildconf --force
will fail to rebuild configure if the date of the files in your extension are older than the current build files (quite likely if you're trying to build an old extension)
To get round this, use
tar -xzmf extname.tgz
(x to extract, z because its a gzipped archive and m to give all new files the current date)
or as the instructions say :-
gzip -d < extname.tgz | tar -xmvf -
Compiling shared PECL extensions with phpize