https://bugs.gentoo.org/933089
https://github.com/libLAS/libLAS/commit/e789d43df4500da0c12d2f6d3ac1d031ed835493

From e789d43df4500da0c12d2f6d3ac1d031ed835493 Mon Sep 17 00:00:00 2001
From: Ben Boeckel <ben.boeckel@kitware.com>
Date: Wed, 31 Oct 2018 11:38:19 -0400
Subject: [PATCH] las2col: use fflush for FILE*

The `fsync` function operates on file descriptors, not C `FILE`
pointers. Instead, use `fflush`.
--- a/apps/las2col.c
+++ b/apps/las2col.c
@@ -1042,7 +1042,7 @@ int main(int argc, char *argv[])
         fflush(files_out[i]);
         if (verbose)
             printf("close file %d\n", i);
-        fsync(files_out[i]);
+        fflush(files_out[i]);
         fclose(files_out[i]);
     }
     free(files_out);