dnfjson: skip sbom tests with dnf5

SBOMs are not yet supported when using the dnf5 solver in
osbuild-depsolve-dnf.  Running the test on Fedora 41, which uses dnf5 by
default, makes the test fail.

Sniff the solver used using a quick, simple depsolve to get the result,
and skip any SBOM tests if the solver is dnf5.

pkg/dnfjson/dnfjson_test.go

@@ -19,6 +19,24 @@ import (
 
 var forceDNF = flag.Bool("force-dnf", false, "force dnf testing, making them fail instead of skip if dnf isn't installed")
 
+// sniffSolverVersion performs a quick depsolve with the given solver to get
+// the value of the underlying library name and version from the 'solver' field
+// in the result.
+func sniffSolverVersion(solver *Solver, repo rpmmd.RepoConfig) string {
+	pkgsets := []rpmmd.PackageSet{
+		{
+			Include:      []string{"filesystem"},
+			Repositories: []rpmmd.RepoConfig{repo},
+		},
+	}
+	res, err := solver.Depsolve(pkgsets, sbom.StandardTypeNone)
+	if err != nil {
+		panic(fmt.Sprintf("sniffSolverVersion: the sniffer failed: %s", err))
+	}
+
+	return res.Solver
+}
+
 func TestDepsolver(t *testing.T) {
 	if !*forceDNF {
 		// dnf tests aren't forced: skip them if the dnf sniff check fails
@@ -114,10 +132,14 @@ func TestDepsolver(t *testing.T) {
 		},
 	}
 
+	solverIsDnf5 := sniffSolverVersion(solver, s.RepoConfig) == "dnf5"
 	for tcName := range testCases {
 		t.Run(tcName, func(t *testing.T) {
 			assert := assert.New(t)
 			tc := testCases[tcName]
+			if tc.sbomType != sbom.StandardTypeNone && solverIsDnf5 {
+				t.Skip("Skipping sbom test with dnf5: unsupported")
+			}
 			pkgsets := make([]rpmmd.PackageSet, len(tc.packages))
 			for idx := range tc.packages {
 				pkgsets[idx] = rpmmd.PackageSet{Include: tc.packages[idx], Repositories: tc.repos, InstallWeakDeps: true}