inject_hash: Convert more Go empty string checks

See https://boringssl-review.googlesource.com/c/boringssl/+/86007

Change-Id: I5e1dbf61e5e98bf7530a5d041613a8ce5c06c5b7
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/86089
Reviewed-by: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
diff --git a/util/fipstools/inject_hash/inject_hash.go b/util/fipstools/inject_hash/inject_hash.go
index a60a0e0..fdd6f4a 100644
--- a/util/fipstools/inject_hash/inject_hash.go
+++ b/util/fipstools/inject_hash/inject_hash.go
@@ -39,10 +39,10 @@
 	var isStatic bool
 	var perm os.FileMode
 
-	if len(arInput) > 0 {
+	if arInput != "" {
 		isStatic = true
 
-		if len(oInput) > 0 {
+		if oInput != "" {
 			return fmt.Errorf("-in-archive and -in-object are mutually exclusive")
 		}
 
@@ -70,7 +70,7 @@
 		for _, contents := range ar {
 			objectBytes = contents
 		}
-	} else if len(oInput) > 0 {
+	} else if oInput != "" {
 		fi, err := os.Stat(oInput)
 		if err != nil {
 			return err
@@ -88,7 +88,7 @@
 	// Hash a different object if specified.
 	var err error
 	hashBytes := objectBytes
-	if len(hashInput) > 0 {
+	if hashInput != "" {
 		hashBytes, err = os.ReadFile(hashInput)
 		if err != nil {
 			return err