Bug 1668910: don't enable Cranelift by default unless target is ARM64 or x86-64. r=lth

These two platforms are the only ones where Cranelift has a functioning
backend. It doesn't make sense to include Cranelift in the build
otherwise, and doing so may cause other issues or breakage.

Differential Revision: https://phabricator.services.mozilla.com/D92284

js/moz.configure

@@ -481,9 +481,9 @@ set_define('MOZ_RUST_SIMD', rust_simd)
 # Support for wasm code generation with Cranelift
 # ==============================================================
 
-@depends(milestone.is_nightly)
-def cranelift_default(is_nightly):
-    if is_nightly:
+@depends(milestone.is_nightly, target)
+def cranelift_default(is_nightly, target):
+    if is_nightly and (target.cpu == 'aarch64' or target.cpu == 'x86_64'):
         return True
 
 js_option('--enable-cranelift',