progress: set --cache-max-size in osbuild

This commit allows controlling the `osbuild --cache-max-size`
option. By default it will set the cache to 20GiB but allows
this to be controlled by the user.

Thanks to Simon for raising this.

bib/pkg/progress/progress.go

@@ -14,6 +14,7 @@ import (
 	"github.com/mattn/go-isatty"
 	"github.com/sirupsen/logrus"
 
+	"github.com/osbuild/images/pkg/datasizes"
 	"github.com/osbuild/images/pkg/osbuild"
 )
 
@@ -319,6 +320,8 @@ type OSBuildOptions struct {
 
 	// BuildLog writes the osbuild output to the given writer
 	BuildLog io.Writer
+
+	CacheMaxSize int64
 }
 
 func writersForOSBuild(pb ProgressBar, opts *OSBuildOptions, internalBuildLog io.Writer) (osbuildStdout io.Writer, osbuildStderr io.Writer) {
@@ -377,12 +380,17 @@ func RunOSBuild(pb ProgressBar, manifest []byte, exports []string, opts *OSBuild
 	defer rp.Close()
 	defer wp.Close()
 
+	cacheMaxSize := int64(20 * datasizes.GiB)
+	if opts.CacheMaxSize != 0 {
+		cacheMaxSize = opts.CacheMaxSize
+	}
 	cmd := exec.Command(
 		osbuildCmd,
 		"--store", opts.StoreDir,
 		"--output-directory", opts.OutputDir,
 		"--monitor=JSONSeqMonitor",
 		"--monitor-fd=3",
+		fmt.Sprintf("--cache-max-size=%v", cacheMaxSize),
 		"-",
 	)
 	for _, export := range exports {

bib/pkg/progress/progress_test.go

@@ -203,3 +203,21 @@ func TestRunOSBuildWithProgressIncorrectJSON(t *testing.T) {
 	assert.EqualError(t, err, `errors parsing osbuild status:
 cannot scan line "invalid-json": invalid character 'i' looking for beginning of value`)
 }
+
+func TestRunOSBuildCacheMaxSize(t *testing.T) {
+	fakeOsbuildBinary := makeFakeOsbuild(t, `echo "$@" > "$0".cmdline`)
+	restore := progress.MockOsbuildCmd(fakeOsbuildBinary)
+	defer restore()
+
+	pbar, err := progress.New("debug")
+	assert.NoError(t, err)
+
+	osbuildOpts := &progress.OSBuildOptions{
+		CacheMaxSize: 77,
+	}
+	err = progress.RunOSBuild(pbar, []byte(`{"fake":"manifest"}`), nil, osbuildOpts)
+	assert.NoError(t, err)
+	cmdline, err := os.ReadFile(fakeOsbuildBinary + ".cmdline")
+	assert.NoError(t, err)
+	assert.Contains(t, string(cmdline), "--cache-max-size=77")
+}