What good would it do you to rebuild your kernel with 'PIPE_BUF' set to
some value other than the number of bytes that one can write to a pipe
Perhaps you are under the mistaken impression that 'PIPE_BUF'
determines how many bytes you can write to a pipe atomically (that is,
that the kernel accesses this value and uses it to influence how pipes
behave). It does not, it only *tells* you how many bytes you can write
to a pipe atomically. If you change it to something else, it will no
longer do so, making it useless.
PIPE_BUF is a consequence of other logic in the kernel, it is not a