The change 699429e60f that allows the
constructor attribute to not be optimized out on gccgo has resulted in a
warning when compiling on the golang compiler.
```
./nsenter.go: In function ‘_cgo_51505a0edd5d_Cfunc_init’:
./nsenter.go:40:49: warning: unused variable ‘a’ [-Wunused-variable]
```
the generated code produced an unused struct like:
```
void
_cgo_d6cfae95ae01_Cfunc_init (void *v)
{
struct
{
char unused;
} __attribute__ ((__packed__, __gcc_struct__)) * a = v;
init ();
}
```
Truly the "fix" would be upstream in cgo. If it knows it is producing an
unused struct, then it should also include __attribute__ ((unused))
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>