sweet/harnesses: log which go-build package fails to build

For golang/go#53572.

Change-Id: I6a90f20d7032b3e2d3989ae7357d0340854b5f64
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/414396
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>
Auto-Submit: Michael Pratt <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>

Author: prattmic

sweet/harnesses/go-build.go

@@ -5,6 +5,7 @@
 package harnesses
 
 import (
+	"fmt"
 	"os/exec"
 	"path/filepath"
 
@@ -91,10 +92,14 @@ func (h GoBuild) Build(cfg *common.Config, bcfg *common.BuildConfig) error {
 		pkgPath := filepath.Join(bcfg.BinDir, bench.name, bench.pkg)
 		dummyBin := filepath.Join(bcfg.BinDir, "dummy")
 		if err := cfg.GoTool().BuildPath(pkgPath, dummyBin); err != nil {
-			return err
+			return fmt.Errorf("error building %s %s: %w", bench.name, bench.pkg, err)
 		}
 	}
-	return cfg.GoTool().BuildPath(bcfg.BenchDir, filepath.Join(bcfg.BinDir, "go-build-bench"))
+
+	if err := cfg.GoTool().BuildPath(bcfg.BenchDir, filepath.Join(bcfg.BinDir, "go-build-bench")); err != nil {
+		return fmt.Errorf("error building go-build tool: %w", err)
+	}
+	return nil
 }
 
 func (h GoBuild) Run(cfg *common.Config, rcfg *common.RunConfig) error {