Use ifunc to dynamically dispatch libc routines for x86

Test: run bionic unit test in aosp_cf_x86_phone emulator
Change-Id: Ib0c0de37cd38d24bfce2dfbe35b8fd8edff004af
diff --git a/libc/arch-x86/atom/string/ssse3-strncat-atom.S b/libc/arch-x86/atom/string/ssse3-strncat-atom.S
index 5618771..ccb08a7 100644
--- a/libc/arch-x86/atom/string/ssse3-strncat-atom.S
+++ b/libc/arch-x86/atom/string/ssse3-strncat-atom.S
@@ -28,7 +28,7 @@
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-#define STRCAT  strncat
+#define STRCAT  strncat_ssse3
 #define USE_AS_STRNCAT
 
 #include "ssse3-strcat-atom.S"