Disable binaryen trap test on Wasm backend (#5877)

* Disable binaryen trap test on Wasm backend

After llvm-mirror/llvm@9f86840#diff-15ffc2fb5830c3a8c3c4c354857b1631, LLVM has two behaviors:
When executing llc with `-mattr=+nontrapping-fptoint`:
It generates nontrapping version of instructions, those with :sat
varient.

When executing llc with `-mattr=-nontrapping-fptoint`:
It generates trapping version of instructions, but it inserts
conditional checks around them so they don't trap and clamp to the
predefined value.

So it seems not very possible to support this trapping test including
three modes (allow, trap, and js) for wasm backend now.

Related: WebAssembly/binaryen/#1168, #5863

Author: aheejin

tests/test_core.py

@@ -7142,6 +7142,7 @@ def test_binaryen(self):
     self.emcc_args += ['-s', 'BINARYEN=1', '-s', 'BINARYEN_METHOD="interpret-binary"']
     self.do_run(open(path_from_root('tests', 'hello_world.c')).read(), 'hello, world!')
 
+  @no_wasm_backend('Wasm backend emits non-trapping float-to-int conversion')
   def test_binaryen_trap_mode(self):
     if not self.is_wasm(): return self.skip('wasm test')
     TRAP_OUTPUTS = ('trap', 'RuntimeError')