fix tests with no deps

Author: mxcl

libexec/stage-test.ts

@@ -44,7 +44,9 @@ const env = await useShellEnv({ installations: [...deps, self] })
 
 if (!yml.test) throw "no `test` node in package.yml"
 
-env['PATH'].push("$PATH")
+if (env['PATH']) {
+  env['PATH'].push("$PATH")
+}
 
 let text = undent`
   #!/usr/bin/env bash

libexec/stage.ts

@@ -53,7 +53,10 @@ const pkg = await pantry.resolve(parse(pkgname))
 /// calc env
 const env = await useShellEnv({ installations: deps })
 if (host().platform == 'darwin') env['MACOSX_DEPLOYMENT_TARGET'] = ['11.0']
-env['PATH'].push("$PATH")
+
+if (env['PATH']) {
+  env['PATH'].push("$PATH")
+}
 
 /// assemble build script
 const pantry_sh = await pantry.getScript(pkg, 'build', deps)