Please make man installation error not fatal

[ale5000-git]

Please make man installation errors not fatal.

Running ./install:

  + install -d /usr/local/bin
  + install _bin/cxx-opt-sh/oils-for-unix.stripped /usr/local/bin/oils-for-unix
    Installed /usr/local/bin/oils-for-unix
    Created 'osh' symlink
    Created 'ysh' symlink
  + install -d /usr/local/share/man/man1
install: chmod 755 /usr/local/share/man/man1: Operation not permitted
  + install -m 644 doc/osh.1 /usr/local/share/man/man1
install: /usr/local/share/man/man1/osh.1: Permission denied
FATAL install error: Couldn't install man page

man page is less important compared to the shell itself.
Isn't a warning enough?