collection: copy CollectionSpec.BTF in Copy()

Without this, loading a copied CollectionSpec fails with:

loading collection: map test: BTF doesn't match collection

Signed-off-by: Timo Beckers <timo@isovalent.com>

collection.go

@@ -45,6 +45,7 @@ func (cs *CollectionSpec) Copy() *CollectionSpec {
 		Maps:      make(map[string]*MapSpec, len(cs.Maps)),
 		Programs:  make(map[string]*ProgramSpec, len(cs.Programs)),
 		ByteOrder: cs.ByteOrder,
+		BTF:       cs.BTF.Copy(),
 	}
 
 	for name, spec := range cs.Maps {

collection_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/cilium/ebpf/asm"
+	"github.com/cilium/ebpf/internal/btf"
 	"github.com/cilium/ebpf/internal/testutils"
 )
 
@@ -66,6 +67,7 @@ func TestCollectionSpecCopy(t *testing.T) {
 				License: "MIT",
 			},
 		},
+		BTF: &btf.Spec{},
 	}
 	cpy := cs.Copy()
 
@@ -80,6 +82,10 @@ func TestCollectionSpecCopy(t *testing.T) {
 	if cpy.Programs["test"] == cs.Programs["test"] {
 		t.Error("Copy returned same Programs")
 	}
+
+	if cpy.BTF == cs.BTF {
+		t.Error("Copy returned same BTF")
+	}
 }
 
 func TestCollectionSpecRewriteMaps(t *testing.T) {