bake: var cmd opt support

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

src/buildx/bake.ts

@@ -44,6 +44,7 @@ export interface BakeCmdOpts {
   sbom?: string;
   source?: string;
   targets?: Array<string>;
+  vars?: Array<string>;
 
   githubToken?: string; // for auth with remote definitions on private repos
 }
@@ -138,6 +139,11 @@ export class Bake {
         args.push('--set', override);
       }
     }
+    if (cmdOpts.vars) {
+      for (const v of cmdOpts.vars) {
+        args.push('--var', v);
+      }
+    }
     if (cmdOpts.allow) {
       for (const allow of cmdOpts.allow) {
         args.push('--allow', allow);