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/strcat.S b/libc/arch-x86/generic/string/strcat.S
index 49e8eee..e2e9623 100644
--- a/libc/arch-x86/generic/string/strcat.S
+++ b/libc/arch-x86/generic/string/strcat.S
@@ -19,7 +19,7 @@
  * cache.
  */
 
-ENTRY(strcat)
+ENTRY(strcat_generic)
 	pushl	%edi			/* save edi */
 	movl	8(%esp),%edi		/* dst address */
 	movl	12(%esp),%edx		/* src address */
@@ -71,4 +71,4 @@
 L2:	popl	%eax			/* pop destination address */
 	popl	%edi			/* restore edi */
 	ret
-END(strcat)
+END(strcat_generic)