Actually don't build lzma on windows.

Change-Id: I539f78c2d8d32ab7561b6f8eab8ff56d7000fb47
diff --git a/build-gdb.sh b/build-gdb.sh
index 4f066c4..c3137a5 100755
--- a/build-gdb.sh
+++ b/build-gdb.sh
@@ -233,9 +233,9 @@
             ;;
     esac
 
-    case "$BH_BUILD_CONFIG" in
-      *windows*)
-        # The liblzma build fails when targeting windows, for some reason.
+    case "$1" in
+      *windows)
+        # The liblzma build fails when targeting windows32, for some reason.
         ;;
 
       *)