Remove unnecessary variables

These are all either recently unused due to the removal of CFLAGS/etc,
or have been exported by Soong and are no longer necessary.

Change-Id: I5930d43fda21acc8202b3d8ea010fbefb6ae4cf1
diff --git a/core/envsetup.mk b/core/envsetup.mk
index 1a79ce2..e798146 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -65,6 +65,7 @@
 HOST_CROSS_OS := windows
 HOST_CROSS_ARCH := x86
 HOST_CROSS_2ND_ARCH := x86_64
+2ND_HOST_CROSS_IS_64_BIT := true
 endif
 
 ifeq ($(HOST_OS),)