ENDBR32 and RDSSPD are multi-byte NOPs on x86-64 processors and
newer x86 processors, starting Pentium Pro. They are UD on older
32-bit processors. Detect this at configure time and adjust the
default value for enable_cet. GCC will enable CET in 32-bit run-time
libraries in any case if --enable-cet is used to configure GCC.
PR target/84148
* config/cet.m4: Check if target support multi-byte NOPS (SSE).
* libatomic/configure: Regenerate.
* libbacktrace/configure: Likewise.
* libgcc/configure: Likewise.
* libgfortran/configure: Likewise.
* libgomp/configure: Likewise.
* libitm/configure: Likewise.
* libmpx/configure: Likewise.
* libobjc/configure: Likewise.
* libquadmath/configure: Likewise.
* libsanitizer/configure: Likewise.
* libssp/configure: Likewise.
* libstdc++-v3/configure: Likewise.
* libvtv/configure: Likewise.
From-SVN: r257809
14e335edc8