AArch64: Linker64 support for AArch64

Addition of support for AArch64 in the linker64 target.

Change-Id: I8dfd9711278f6706063e91f626b6007ea7a3dd6e
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>
diff --git a/libc/arch-x86_64/include/machine/exec.h b/libc/arch-x86_64/include/machine/exec.h
index 6d16439..829351c 100644
--- a/libc/arch-x86_64/include/machine/exec.h
+++ b/libc/arch-x86_64/include/machine/exec.h
@@ -12,7 +12,7 @@
 
 #define ELF_TARG_CLASS		ELFCLASS64
 #define ELF_TARG_DATA		ELFDATA2LSB
-#define ELF_TARG_MACH		EM_AMD64
+#define ELF_TARG_MACH		EM_X86_64
 
 #define _NLIST_DO_ELF
 #define _KERN_DO_ELF64