feat(release): add @[Release] attribute and --release CLI flag

- @[Release] disables borrow checking and bounds checking in the function
- --release passes -O3 -flto to the C compiler for optimized builds
- Selfhost loop still deterministic

src/ast.bux

@@ -275,6 +275,7 @@ struct Decl {
     isAsync: bool,
     isChecked: int,          // @[Checked] attribute (0/1)
     isDrop: int,             // @[Drop] attribute (0/1)
+    isRelease: int,          // @[Release] attribute (0/1)
     // Names
     strValue: String,        // decl name
     strValue2: String,       // interface name, dll name, module path