kernel: on OL6 only, simulate the gcc 4.4 kABI for __stack_chk_fail()

kernel: on OL6 only, simulate the gcc 4.4 kABI for __stack_chk_fail()

The __visible linkage changes st_value calculation for genksyms on newer
compilers such as OL7's 4.8 and SCL's 4.9. However, this symbol is in
the kABI whitelist and needs to retain its old st_value, even though the
guts of the compiled function have not changed.

Add a special directive, CONFIG_SIMULATE_GCC44_KABI, which will mask the
__visible qualifier at genksyms time; and use it only on OL6 builds.

Orabug: 27509351
Signed-off-by: Todd Vierling <todd.vierling@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>