testing: run cleanups after exiting a benchmark run

This is important, otherwise temporary directories don't get removed.

Issue found while working on Go 1.20 support.

interp/interpreter.go

@@ -577,7 +577,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 						// runtime instead of at compile time. But we need to
 						// revert any changes made by the call first.
 						if r.debug {
-							fmt.Fprintln(os.Stderr, indent+"!! revert because of error:", callErr.Err)
+							fmt.Fprintln(os.Stderr, indent+"!! revert because of error:", callErr.Error())
 						}
 						callMem.revert()
 						err := r.runAtRuntime(fn, inst, locals, &mem, indent)

src/machine/board_fe310.go

@@ -15,8 +15,8 @@ const (
 	P09 Pin = 9
 	P10 Pin = 10
 	P11 Pin = 11
-	P12 Pin = 12
-	P13 Pin = 13
+	P12 Pin = 12 // peripherals: I2C0 SDA
+	P13 Pin = 13 // peripherals: I2C0 SCL
 	P14 Pin = 14
 	P15 Pin = 15
 	P16 Pin = 16

src/testing/benchmark.go

@@ -159,6 +159,7 @@ func (b *B) ReportAllocs() {
 
 // runN runs a single benchmark for the specified number of iterations.
 func (b *B) runN(n int) {
+	b.runCleanup() // start fresh in the next iteration
 	b.N = n
 	runtime.GC()
 	b.ResetTimer()
@@ -457,6 +458,7 @@ func (b *B) Run(name string, f func(b *B)) bool {
 		// Only process sub-benchmarks, if any.
 		sub.hasSub = true
 	}
+	defer sub.runCleanup() // make sure all cleanups are run, even when panicking
 	if sub.run1() {
 		sub.run()
 	}