x86_64: Add targets

This is required to continue builds of other projects.

Change-Id: Id3f5c54a7dabce0f67f54e58c161c3fad9be417e
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>
diff --git a/Libffi.mk b/Libffi.mk
index e92fb32..7807b56 100644
--- a/Libffi.mk
+++ b/Libffi.mk
@@ -34,6 +34,10 @@
   LOCAL_SRC_FILES := src/x86/ffi.c src/x86/sysv.S
 endif
 
+ifeq ($(ffi_os)-$(ffi_arch),linux-x86_64)
+  LOCAL_SRC_FILES := src/x86/ffi64.c src/x86/unix64.S
+endif
+
 ifeq ($(ffi_os)-$(ffi_arch),darwin-x86)
   LOCAL_SRC_FILES := src/x86/ffi.c src/x86/darwin.S
 endif