makefile: update CPPFLAGS & CFLAGS

[clan]

1. _FORTIFY_SOURCE is defined built-in by compiler, so undefine the define to slience warnings like:

: warning: "_FORTIFY_SOURCE" redefined
: note: this is the location of the previous definition

2. -Wno-unknown-warning-option & -Wno-gnu-alignof-expression are available for clang only, but "-fplan9-extensions" is used which is gcc only! So remove these two warning options to avoid:

cc1: note: unrecognized command-line option ‘-Wno-gnu-alignof-expression’ may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option ‘-Wno-unknown-warning-option’ may have been intended to silence earlier diagnostics

[lahwaacz]

Where do you get warning: "_FORTIFY_SOURCE" redefined ? The documentation for GCC at least says nothing about the need to undefine it: https://www.gnu.org/software/libc/manual/html_node/Source-Fortification.html

[clan]

Where do you get warning: "_FORTIFY_SOURCE" redefined ? The documentation for GCC at least says nothing about the need to undefine it: https://www.gnu.org/software/libc/manual/html_node/Source-Fortification.html

see: SELinuxProject/selinux@4f96b32
and discussion here: https://patchwork.kernel.org/project/selinux/patch/[email protected]/

I encoutered this warning when compilng in Gentoo Hardened profile.

[github-actions]

This PR is stale because it has been open 90 days with no activity. This PR will be closed in 30 days unless new comments are made or the stale label is removed. To skip these checks, apply the "lifecycle/frozen" label.