dockerfile: heredoc should use 0644 permissions

Previously, it appears the permissions were 0664, which seems to be a
typo of the above - there's no real reason for these permissions to be
higher, so we can bring them down to be consistent with everywhere else
we create files.

Signed-off-by: Justin Chadwell <[email protected]>

Author: jedevc

frontend/dockerfile/dockerfile2llb/convert.go

@@ -1159,7 +1159,7 @@ func dispatchCopy(d *dispatchState, cfg copyConfig) error {
 		data := src.Data
 		f := src.Path
 		st := llb.Scratch().File(
-			llb.Mkfile(f, 0664, []byte(data)),
+			llb.Mkfile(f, 0644, []byte(data)),
 			dockerui.WithInternalName("preparing inline document"),
 		)