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-strncmp-atom.S b/libc/arch-x86/atom/string/ssse3-strncmp-atom.S
index 4762d7e..2bf5002 100644
--- a/libc/arch-x86/atom/string/ssse3-strncmp-atom.S
+++ b/libc/arch-x86/atom/string/ssse3-strncmp-atom.S
@@ -30,6 +30,6 @@
 
 
 #define USE_AS_STRNCMP
-#define STRCMP  strncmp
+#define STRCMP  strncmp_ssse3
 #include "ssse3-strcmp-atom.S"