configure.ac: fix stack-protector detection

[fabrice]

Use AC_LINK_IFELSE instead of AC_COMPILE_IFELSE to check for
stack-protector availability as some compilers could missed the needed
library (-lssp or -lssp_nonshared) at linking step:

/home/giuliobenetti/autobuild/run/instance-3/output-1/host/bin/x86_64-linux-g++ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -Wall -W -Wformat=2 -fstack-protector-strong -o smartctl smartctl.o atacmdnames.o atacmds.o ataidentify.o ataprint.o dev_ata_cmd_set.o dev_intelliprop.o dev_interface.o dev_jmb39x_raid.o json.o knowndrives.o nvmecmds.o nvmeprint.o scsicmds.o scsiata.o scsinvme.o scsiprint.o utility.o os_linux.o cciss.o dev_areca.o -lselinux
/home/giuliobenetti/autobuild/run/instance-3/output-1/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-uclibc/8.3.0/../../../../x86_64-buildroot-linux-uclibc/bin/ld: cannot find -lssp_nonshared
/home/giuliobenetti/autobuild/run/instance-3/output-1/host/opt/ext-toolchain/bin/../lib/gcc/x86_64-buildroot-linux-uclibc/8.3.0/../../../../x86_64-buildroot-linux-uclibc/bin/ld: cannot find -lssp

Fixes:

• ​http://autobuild.buildroot.org/results/0de9f2a69fa2a39164211299f8a429d2fec6935a

[fabrice]

Patch

[Christian Franke]

Patch applied in r5032, thanks!