client: allow exposing fsutil.FS through SolveOpts

This completes propogating the fsutil.FS abstraction into the SolveOpt,
deprecating the old LocalDirs.

Since this is entirely a golang-level abstraction, we could potentially
investigate just removing the old LocalDirs directly.

Signed-off-by: Justin Chadwell <me@jedevc.com>

client/solve.go

@@ -35,7 +35,8 @@ import (
 
 type SolveOpt struct {
 	Exports               []ExportEntry
-	LocalDirs             map[string]string
+	LocalDirs             map[string]string // Deprecated: use LocalFiles
+	LocalFiles            map[string]fsutil.FS
 	OCIStores             map[string]content.Store
 	SharedKey             string
 	Frontend              string
@@ -90,7 +91,19 @@ func (c *Client) solve(ctx context.Context, def *llb.Definition, runGateway runG
 		return nil, errors.New("invalid with def and cb")
 	}
 
-	syncedDirs, err := prepareSyncedFiles(def, opt.LocalDirs)
+	sourceFS := make(map[string]fsutil.FS)
+	for k, fs := range opt.LocalFiles {
+		sourceFS[k] = fs
+	}
+	for k, dir := range opt.LocalDirs {
+		fs, err := fsutil.NewFS(dir)
+		if err != nil {
+			return nil, err
+		}
+		sourceFS[k] = fs
+	}
+
+	syncedDirs, err := prepareSyncedFiles(def, sourceFS)
 	if err != nil {
 		return nil, err
 	}
@@ -361,16 +374,7 @@ func (c *Client) solve(ctx context.Context, def *llb.Definition, runGateway runG
 	return res, nil
 }
 
-func prepareSyncedFiles(def *llb.Definition, localDirs map[string]string) (filesync.StaticDirSource, error) {
-	localFiles := make(map[string]fsutil.FS)
-	for name, d := range localDirs {
-		fs, err := fsutil.NewFS(d)
-		if err != nil {
-			return nil, err
-		}
-		localFiles[name] = fs
-	}
-
+func prepareSyncedFiles(def *llb.Definition, localFiles map[string]fsutil.FS) (filesync.StaticDirSource, error) {
 	resetUIDAndGID := func(p string, st *fstypes.Stat) fsutil.MapResult {
 		st.Uid = 0
 		st.Gid = 0