Support for building/using tblgen for Windows SDK.

Change-Id: I174939e0acb4bc3bea368c8a8e8435384bcc8d48
diff --git a/llvm.mk b/llvm.mk
index d5a7878..badc445 100644
--- a/llvm.mk
+++ b/llvm.mk
@@ -2,7 +2,7 @@
 $(error Must set variable LLVM_ROOT_PATH before including this! $(LOCAL_PATH))
 endif
 
-TBLGEN := $(HOST_OUT_EXECUTABLES)/tblgen$(HOST_EXECUTABLE_SUFFIX)
+TBLGEN := $(BUILD_OUT_EXECUTABLES)/tblgen$(BUILD_EXECUTABLE_SUFFIX)
 
 CLEAR_TBLGEN_VARS := $(LLVM_ROOT_PATH)/clear_tblgen_vars.mk
 LLVM_HOST_BUILD_MK := $(LLVM_ROOT_PATH)/llvm-host-build.mk