[wasm-ctor-eval] Do not error on non-constant code in the start function (#8778)

Before, we did not catch the Nonconstant exception.

src/tools/wasm-ctor-eval.cpp

diff --git a/src/tools/wasm-ctor-eval.cpp b/src/tools/wasm-ctor-eval.cpp
index 0dbeb57..b503b0a 100644
--- a/src/tools/wasm-ctor-eval.cpp
+++ b/src/tools/wasm-ctor-eval.cpp
@@ -1485,11 +1485,16 @@
       }
     }
   } catch (FailToEvalException& fail) {
-    // that's it, we failed to even create the instance
+    // That's it, we failed to even create the instance.
     if (!quiet) {
       std::cout << "  ...stopping since could not create module instance: "
                 << fail.why << "\n";
     }
+  } catch (NonconstantException& fail) {
+    // We can also fail during start due to a non-constant operation.
+    if (!quiet) {
+      std::cout << "  ...stopping since non-constant in start\n";
+    }
   } catch (TopologicalSort::CycleException e) {
     // We use a topological sort for GC globals. If there is a non-breakable
     // cycle there, we will hit an error (we can break cycles in nullable and

test/lit/ctor-eval/start-nonconstant.wast

diff --git a/test/lit/ctor-eval/start-nonconstant.wast b/test/lit/ctor-eval/start-nonconstant.wast
new file mode 100644
index 0000000..4d6baa6
--- /dev/null
+++ b/test/lit/ctor-eval/start-nonconstant.wast
@@ -0,0 +1,38 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: foreach %s %t wasm-ctor-eval --ctors=test --kept-exports=test --quiet -all -S -o - | filecheck %s
+
+;; A non-constant (relaxed SIMD) operation in the start function. We should not
+;; error.
+(module
+ ;; CHECK:      (type $0 (func (param v128)))
+
+ ;; CHECK:      (type $1 (func))
+
+ ;; CHECK:      (import "a" "b" (func $import (type $0) (param v128)))
+ (import "a" "b" (func $import (param v128)))
+
+ ;; CHECK:      (export "test" (func $0))
+ (export "test" (func $0))
+
+ ;; CHECK:      (start $0)
+ (start $0)
+
+ ;; CHECK:      (func $0 (type $1)
+ ;; CHECK-NEXT:  (call $import
+ ;; CHECK-NEXT:   (f32x4.relaxed_min
+ ;; CHECK-NEXT:    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+ ;; CHECK-NEXT:    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $0
+  ;; The import avoids vacuum from removing the entire body.
+  (call $import
+   (f32x4.relaxed_min
+    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+    (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000)
+   )
+  )
+ )
+)
+