allow building with a wasi stack built with llvm22

adapted from https://hg-edge.mozilla.org/mozilla-central/rev/b1b4f0d7ed12
--- build/moz.configure/toolchain.configure.orig
+++ build/moz.configure/toolchain.configure
@@ -1122,7 +1122,7 @@ def compiler_wrapper(wrapper, ccache):
 
 @dependable
 def wasm():
-    return split_triplet("wasm32-wasi", allow_wasi=True)
+    return split_triplet("wasm32-wasip1", allow_wasi=True)
 
 
 @template
