runtime: for FFI, treat directIface types as pointers

    
    This only matters on systems that pass a struct with a single pointer
    field differently than passing a single pointer.  I noticed it on
    32-bit PPC, where the reflect package TestDirectIfaceMethod failed.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/195878

From-SVN: r275814

gcc/go/gofrontend/MERGE

-7aabaf8623cf88e2378057476a034093abbe5aab
+09ca3c1ea8a52b5d3d6c4331c59d44e0b6bfab57
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/runtime/ffi.go

@@ -224,6 +224,9 @@ func structToFFI(typ *structtype) *__ffi_type {
 	if c == 0 {
 		return emptyStructToFFI()
 	}
+	if typ.typ.kind&kindDirectIface != 0 {
+		return ffi_type_pointer()
+	}
 
 	fields := make([]*__ffi_type, 0, c+1)
 	checkPad := false
@@ -307,6 +310,9 @@ func arrayToFFI(typ *arraytype) *__ffi_type {
 	if typ.len == 0 {
 		return emptyStructToFFI()
 	}
+	if typ.typ.kind&kindDirectIface != 0 {
+		return ffi_type_pointer()
+	}
 	elements := make([]*__ffi_type, typ.len+1)
 	et := typeToFFI(typ.elem)
 	for i := uintptr(0); i < typ.len; i++ {