hi, congratulations on this project, we have a framework and were considering implementing something like this, so we're really happy to have found your project.

the issue is, we have our vendor dir in the root dir of the project, and our build files in a build dir like this

composer

composer file

{
	[...]
	"autoload": {
		"psr-4": {
			"[..]\\": "../src/"
		}
	},
	"config": {
		"vendor-dir": "../vendor/"
	},
	"scripts": {
		"prefix-namespaces": [
			"strauss",
			"@php composer dump-autoload"
		],
		"post-install-cmd": [
			"@prefix-namespaces"
		],
		"post-update-cmd": [
			"@prefix-namespaces"
		]
	},
	[...]
	"require-dev": {
		"brianhenryie/strauss": "^0.20.1"
	}
}

root dir
...
├── build                              # Files needed to build the project
│   ├── composer.json
│   ...
...
...
├── src                                # PHP files
│   ├── Project.php
│   ...
...
├── vendor                             # PHP dependencies

and so we get a

i followed the trail and flysystem throws this error. i tried to concat work dir with the vendor-dir and fool it, and even skipping flysystem all together, but it only got so far, and no changes where written in the end.
i saw #133 too.

im willing to help!