MockGen header comment: trim .exe suffix on Windows (#119)

To address #118

---------

Co-authored-by: Marten Seemann <martenseemann@gmail.com>

mockgen/mockgen.go

@@ -31,6 +31,7 @@ import (
 	"os/exec"
 	"path"
 	"path/filepath"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -316,7 +317,11 @@ func (g *generator) Generate(pkg *model.Package, outputPkgName string, outputPac
 	g.p("// Generated by this command:")
 	g.p("//")
 	// only log the name of the executable, not the full path
-	g.p("//\t%v", strings.Join(append([]string{filepath.Base(os.Args[0])}, os.Args[1:]...), " "))
+	name := filepath.Base(os.Args[0])
+	if runtime.GOOS == "windows" {
+		name = strings.TrimSuffix(name, ".exe")
+	}
+	g.p("//\t%v", strings.Join(append([]string{name}, os.Args[1:]...), " "))
 	g.p("//")
 
 	// Get all required imports, and generate unique names for them all.