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-strcpy-atom.S b/libc/arch-x86/atom/string/ssse3-strcpy-atom.S
index 3690b0d..45b0c02 100644
--- a/libc/arch-x86/atom/string/ssse3-strcpy-atom.S
+++ b/libc/arch-x86/atom/string/ssse3-strcpy-atom.S
@@ -81,7 +81,7 @@
 # define POP(REG)	popl REG; CFI_POP (REG)
 
 # ifndef STRCPY
-#  define STRCPY  strcpy
+#  define STRCPY  strcpy_atom
 # endif
 
 # ifdef USE_AS_STRNCPY