Fix relative path of bpf modules

Using bpf as test data installs the module into a strange
subdirectory, clear the Rel() value before exporting it as
a SourceFileProducer.

Bug: 130206035
Test: m vts_test_binary_bpf_module
Change-Id: Ifdae90d11b15d65c097562d7d6985a8a1dca2bfd

bpf/bpf.go

@@ -91,7 +91,7 @@ func (bpf *bpf) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 			},
 		})
 
-		bpf.objs = append(bpf.objs, obj)
+		bpf.objs = append(bpf.objs, obj.WithoutRel())
 	}
 }