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-wmemcmp-atom.S b/libc/arch-x86/atom/string/ssse3-wmemcmp-atom.S
index 2c3fa02..a81b78b 100644
--- a/libc/arch-x86/atom/string/ssse3-wmemcmp-atom.S
+++ b/libc/arch-x86/atom/string/ssse3-wmemcmp-atom.S
@@ -28,7 +28,7 @@
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-#define MEMCMP  wmemcmp
+#define MEMCMP  wmemcmp_atom
 
 #define USE_WCHAR
 #define USE_AS_WMEMCMP 1