x86/CET: Build target libraries with -mshstk

With revision 259522:

commit d59cfa9a4064339cf2bd2da828c4c133f13e57f0
Author: hjl <hjl@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri Apr 20 13:30:13 2018 +0000

    Define __CET__ for -fcf-protection and remove -mibt

-mcet becomes an alias for -mshstk.

	PR target/85485
	* cet.m4 (GCC_CET_FLAGS): Replace -mcet with -mshstk.

From-SVN: r259608

config/ChangeLog

+2018-04-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/85485
+	* cet.m4 (GCC_CET_FLAGS): Replace -mcet with -mshstk.
+
 2018-04-19  Jakub Jelinek  <jakub@redhat.com>
 
-	* config/cet.m4 (GCC_CET_FLAGS): Default to --disable-cet, replace
+	* cet.m4 (GCC_CET_FLAGS): Default to --disable-cet, replace
 	--enable-cet=default with --enable-cet=auto.
 
 2018-04-18  David Malcolm  <dmalcolm@redhat.com>

config/cet.m4

@@ -42,7 +42,7 @@ asm ("setssbsy");
     ;;
 esac
 if test x$enable_cet = xyes; then
-  $1="-fcf-protection -mcet"
+  $1="-fcf-protection -mshstk"
   AC_MSG_RESULT([yes])
 else
   AC_MSG_RESULT([no])