X Fix build on old GCC

Similarly to pygolang@77719d8a

bigfile/file_zodb.cpp

@@ -73,8 +73,14 @@ static void zfile_munmap(VMA *vma, BigFile *file) {
 
 // NOTE reusing whole bigfile_ops for just .mmap* ops.
 extern const bigfile_ops ZBigFile_mmap_ops;
-const bigfile_ops ZBigFile_mmap_ops = {
-    .mmap_setup_read    = zfile_mmap_setup_read,
-    .remmap_blk_read    = zfile_remmap_blk_read,
-    .munmap             = zfile_munmap,
+static bigfile_ops _mkZBigFile_mmap_ops() {
+    // workaround for "sorry, unimplemented: non-trivial designated initializers not supported"
+    bigfile_ops _;
+    _.mmap_setup_read   = zfile_mmap_setup_read;
+    _.remmap_blk_read   = zfile_remmap_blk_read;
+    _.munmap            = zfile_munmap;
+    _.loadblk  = NULL;
+    _.storeblk = NULL;
+    return _;
 };
+const bigfile_ops ZBigFile_mmap_ops = _mkZBigFile_mmap_ops();

wcfs/internal/wcfs_watchlink.h

@@ -58,7 +58,7 @@ struct rxPkt {
     error  from_string(const string& rx);
     string to_string() const;
 };
-static_assert(sizeof(rxPkt) == 256);    // NOTE 128 is too low for long error message
+static_assert(sizeof(rxPkt) == 256, "rxPkt miscompiled");   // NOTE 128 is too low for long error message
 
 
 // WatchLink represents /head/watch link opened on wcfs.