tint/cmd: Use correct preprocessor guard for libspriv.hpp

This header is used by TINT_BUILD_SPV_READER not TINT_BUILD_SPV_WRITER

Change-Id: Ia42e4f2bf2ad37f426d2bf14e962abed9de147a9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/122520
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/src/tint/cmd/helper.cc b/src/tint/cmd/helper.cc
index 53013fe..49b970a 100644
--- a/src/tint/cmd/helper.cc
+++ b/src/tint/cmd/helper.cc
@@ -18,7 +18,7 @@
 #include <utility>
 #include <vector>
 
-#if TINT_BUILD_SPV_WRITER
+#if TINT_BUILD_SPV_READER
 #include "spirv-tools/libspirv.hpp"
 #endif