Ensure user trap code 0 is never used

Cranelift will return None from TrapCode::user(0).

Fixes rust-lang/rustc_codegen_cranelift#1548

Author: bjorn3

src/inline_asm.rs

@@ -136,7 +136,7 @@ pub(crate) fn codegen_inline_asm_terminator<'tcx>(
             fx.bcx.ins().jump(destination_block, &[]);
         }
         None => {
-            fx.bcx.ins().trap(TrapCode::user(0 /* unreachable */).unwrap());
+            fx.bcx.ins().trap(TrapCode::user(1 /* unreachable */).unwrap());
         }
     }
 }

src/intrinsics/simd.rs

@@ -1136,7 +1136,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
         _ => {
             fx.tcx.dcx().span_err(span, format!("Unknown SIMD intrinsic {}", intrinsic));
             // Prevent verifier error
-            fx.bcx.ins().trap(TrapCode::user(0 /* unreachable */).unwrap());
+            fx.bcx.ins().trap(TrapCode::user(1 /* unreachable */).unwrap());
             return;
         }
     }