config.mak.uname: add a note about NO_STRLCPY for Linux

config.mak.uname: add a note about NO_STRLCPY for Linux

Commit 817151e61a ("Rename safe_strncpy() to strlcpy().", 2006-06-24)
added the NO_STRLCPY make variable to allow the conditional use of
the gitstrlcpy() compat function on those platforms which didn't
provide the 'standard' strlcpy() function.

Recently, in the summer of 2023, the strlcpy() and strlcat() functions
were added to the glibc library (v2.38), so some of the more up-to-date
Linux distributions no longer need to set NO_STRLCPY. For example, both
Ubuntu 24.04 LTS and RHEL 10 beta have glibc v2.39. However, several
distributions, which are still within their support window, have an
earlier version and must still use the 'compat' version of strlcpy().

If the meson or autoconf build systems are used on newer platforms, then
they will be configured to to use strlcpy() from glibc, whereas the make
build will always choose the 'compat' function instead. Add a note to
the config.mak.uname file, in the Linux section, to prompt make users to
override NO_STRLCPY in the config.mak file, if appropriate.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>