security hardening: add support for glibc _FORTIFY_SOURCE=3

security hardening: add support for glibc _FORTIFY_SOURCE=3

A new _FORTIFY_SOURCE=3 level was introduced in glibc, in commit:
https://sourceware.org/git/?p=glibc.git;a=commit;h=c43c5796121bc5bcc0867f02e5536874aa8196c1

This commit was first included glibc 2.33. At that time, it was only
supported by llvm/clang 9, and not by any released gcc version.

To support _FORTIFY_SOURCE=3, the needed gcc features were introduced
in version 12. The gcc 12 support was added in glibc commit:
https://sourceware.org/git/?p=glibc.git;a=commit;h=86bf0feb0e3ec8e37872f72499d6ae33406561d7
This commit was first included in glibc 2.35.

Buildroot updated to glibc 2.35 in commit:
https://git.buildroot.org/buildroot/commit/?id=68d0aede597d32816c5b2ff32de0ce33cc14eb93

Buildroot introduced gcc 12 support in commit:
https://git.buildroot.org/buildroot/commit/?id=0f1ad4fc93286adaba852c99d6e1c2565b5c4258

Support for _FORTIFY_SOURCE=3 can now be added.

Signed-off-by: Julien Olivain <[email protected]>
Signed-off-by: Yann E. MORIN <[email protected]>