[embedded] Fix fatalError() to produce a trap in Release configurations

Author: kubamracek

stdlib/public/core/Assert.swift

@@ -281,8 +281,11 @@ public func fatalError(
   if _isDebugAssertConfiguration() {
     _assertionFailure("Fatal error", message(), file: file, line: line,
       flags: _fatalErrorFlags())
+  } else {
+    Builtin.condfail_message(true._value,
+      StaticString("fatal error").unsafeRawPointer)
+    Builtin.unreachable()
   }
-  _conditionallyUnreachable()
 }
 #endif
 

test/embedded/traps-fatalerror-ir.swift

@@ -23,5 +23,7 @@ public func test() {
 
 // CHECK-NOMESSAGE:      define {{.*}}void @"$s4main4testyyF"(){{.*}} {
 // CHECK-NOMESSAGE-NEXT: entry:
+// CHECK-NOMESSAGE-NEXT:   tail call void asm sideeffect "", "n"(i32 0)
+// CHECK-NOMESSAGE-NEXT:   tail call void @llvm.trap()
 // CHECK-NOMESSAGE-NEXT:   unreachable
 // CHECK-NOMESSAGE-NEXT: }