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/generic/string/strncmp.S b/libc/arch-x86/generic/string/strncmp.S
index 9ba83a1..6d9f23c 100644
--- a/libc/arch-x86/generic/string/strncmp.S
+++ b/libc/arch-x86/generic/string/strncmp.S
@@ -12,7 +12,7 @@
  * cache.
  */
 
-ENTRY(strncmp)
+ENTRY(strncmp_generic)
 	pushl	%ebx
 	movl	8(%esp),%eax
 	movl	12(%esp),%ecx
@@ -111,4 +111,4 @@
 L4:	xorl	%eax,%eax
 	popl	%ebx
 	ret
-END(strncmp)
+END(strncmp_generic)