treewide: remove unnecessary use of fmt.Sprint

Change-Id: I619dcf56665365e09be27e7c58b8b3596715b8b4
Reviewed-on: https://review.monogon.dev/c/monogon/+/3016
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Vouch-Run-CI: Tim Windelschmidt <tim@monogon.tech>
diff --git a/metropolis/build/gotoolwrap/main.go b/metropolis/build/gotoolwrap/main.go
index 3c871c1..d2645ce 100644
--- a/metropolis/build/gotoolwrap/main.go
+++ b/metropolis/build/gotoolwrap/main.go
@@ -136,11 +136,11 @@
 	defer os.RemoveAll(tempDir)
 
 	cmd.Env = append(cmd.Env,
-		fmt.Sprintf("GOROOT=%s", gorootAbs),
-		fmt.Sprintf("GOPATH=%s", gopathAbs),
-		fmt.Sprintf("PATH=%s", path),
-		fmt.Sprintf("GO111MODULE=off"),
-		fmt.Sprintf("GOCACHE=%s", tempDir),
+		"GOROOT=" + gorootAbs,
+		"GOPATH=" + gopathAbs,
+		"PATH=" + path,
+		"GO111MODULE=off",
+		"GOCACHE=" + tempDir,
 	)
 
 	// Run the command interactively.