gdc latest Cygwin

[tdm3j2bqz]

This is from a regular Cygwin package called gcc-gdc installed 
after the gcc-core package was installed.
```
$ gdc hello.d -o hello
d21: error: cannot find source code for runtime library file 
'object.d'
d21: note: dmd might not be correctly installed. Run 'dmd -man' 
for installation instructions.
d21: note: config file: not found

$ dmd
-bash: dmd: command not found

$ which gdc
/usr/bin/gdc

$ gdc --version
gdc (GCC) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  
There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A 
PARTICULAR PURPOSE.
```
Is gdc known to work on Cygwin?