Fix call to system fallocate to handle errno correctly.

2021-03-19  Holger Berger  <holger.berger@googlemail.com>

gold/
	PR gold/26541
	* output.cc (gold_fallocate): Use errno when calling system fallocate.

gold/ChangeLog

@@ -1,3 +1,8 @@
+2021-03-19  Holger Berger  <holger.berger@googlemail.com>
+
+	PR gold/26541
+	* output.cc (gold_fallocate): Use errno when calling system fallocate.
+
 2021-03-19  Cary Coutant  <ccoutant@gmail.com>
 
 	PR gold/26585

gold/output.cc

@@ -141,12 +141,14 @@ gold_fallocate(int o, off_t offset, off_t len)
 
 #ifdef HAVE_FALLOCATE
   {
+    errno = 0;
     int err = ::fallocate(o, 0, offset, len);
-    if (err != EINVAL && err != ENOSYS && err != EOPNOTSUPP)
-      return err;
+    if (err < 0 && errno != EINVAL && errno != ENOSYS && errno != EOPNOTSUPP)
+      return errno;
   }
 #endif // defined(HAVE_FALLOCATE)
 
+  errno = 0;
   if (::ftruncate(o, offset + len) < 0)
     return errno;
   return 0;