Don't print opt fuel messages to stdout because it breaks Rustbuild

src/librustc/session/mod.rs

@@ -868,7 +868,7 @@ impl Session {
                 let fuel = self.optimization_fuel_limit.get();
                 ret = fuel != 0;
                 if fuel == 0 && !self.out_of_fuel.get() {
-                    println!("optimization-fuel-exhausted: {}", msg());
+                    eprintln!("optimization-fuel-exhausted: {}", msg());
                     self.out_of_fuel.set(true);
                 } else if fuel > 0 {
                     self.optimization_fuel_limit.set(fuel - 1);

src/librustc_driver/lib.rs

@@ -944,7 +944,7 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
             control.compilation_done.callback = box move |state| {
                 old_callback(state);
                 let sess = state.session;
-                println!("Fuel used by {}: {}",
+                eprintln!("Fuel used by {}: {}",
                     sess.print_fuel_crate.as_ref().unwrap(),
                     sess.print_fuel.get());
             }

src/test/run-pass/optimization-fuel-0.rs

@@ -12,7 +12,8 @@
 
 use std::mem::size_of;
 
-// compile-flags: -Z fuel=foo=0
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z fuel=foo=0
 
 struct S1(u8, u16, u8);
 struct S2(u8, u16, u8);

src/test/run-pass/optimization-fuel-1.rs

@@ -12,7 +12,8 @@
 
 use std::mem::size_of;
 
-// compile-flags: -Z fuel=foo=1
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z fuel=foo=1
 
 struct S1(u8, u16, u8);
 struct S2(u8, u16, u8);

src/test/ui/print-fuel/print-fuel.rs

@@ -11,7 +11,8 @@
 #![crate_name="foo"]
 #![allow(dead_code)]
 
-// compile-flags: -Z print-fuel=foo
+// (#55495: The --error-format is to sidestep an issue in our test harness)
+// compile-flags: --error-format human -Z print-fuel=foo
 // compile-pass
 
 struct S1(u8, u16, u8);