Always specify default SDK version

Without the pulumi java dependency the SDK is not buildable. We can't infer this at build time because go modules don't have a 'build phase' and can't lookup their own version.

pkg/codegen/java/gen.go

@@ -13,13 +13,17 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/blang/semver"
 	"github.com/pulumi/pulumi/pkg/v3/codegen"
 	"github.com/pulumi/pulumi/pkg/v3/codegen/schema"
 	"github.com/pulumi/pulumi/sdk/v3/go/common/util/contract"
 
 	"github.com/pulumi/pulumi-java/pkg/codegen/java/names"
 )
 
+// This should be bumped as required at the point of release.
+var DEFAULT_SDK_VERSION = semver.Version{Major: 0, Minor: 18, Patch: 0}
+
 func packageName(packages map[string]string, name string) string {
 	if pkg, ok := packages[name]; ok {
 		return pkg
@@ -2039,7 +2043,9 @@ func generateModuleContextMap(tool string, pkg *schema.Package) (map[string]*mod
 					panic(fmt.Sprintf("Failed to cast `pkg.Language[\"java\"]`=%v to `PackageInfo`", raw))
 				}
 			}
-			javaInfo = javaInfo.WithDefaultDependencies()
+			javaInfo = javaInfo.
+				WithDefaultDependencies().
+				WithJavaSdkDependencyDefault(DEFAULT_SDK_VERSION)
 			info = &javaInfo
 			infos[def] = info
 		}