Import files not working

[joan38]

Related to #4524

Reproduce

mkdir mill-issue-4618 && cd $_
curl -L https://repo1.maven.org/maven2/com/lihaoyi/mill-dist/0.13.0-M0/mill -o mill && chmod +x mill

cat > .mill-version <<EOF
0.13.0-M0-95-606de3
EOF

cat > build.mill <<EOF
package build

import mill.*

object \`package\` extends RootModule with SparkConfig
EOF

cat > MyJob.mill <<EOF
package build

trait MyJob extends SparkConfig
EOF

cat > SparkConfig.mill <<EOF
package build

trait SparkConfig extends mill.Module
EOF

./mill clean
[build.mill-62/66] compile
[build.mill-62] [info] compiling 3 Scala sources to /.../mill-issue-4618/out/mill-build/compile.dest/classes ...
[build.mill-62] [error] -- [E6] /.../mill-issue-4618/MyJob.mill:3:21
[build.mill-62] [error] 3 │trait MyJob extends SparkConfig
[build.mill-62] [error]   │                    ^^^^^^^^^^^
[build.mill-62] [error]   │Not found: type SparkConfig
[build.mill-62] [warn] -- /.../mill-issue-4618/build.mill:9:1
[build.mill-62] [warn] Line is indented too far to the left, or a `}` is missing
[build.mill-62] [warn] one warning found
[build.mill-62] [error] one error found

Thanks

[lihaoyi]

@joan38 could you minimize it further?

[joan38]

Done.
I was actually trying to report some cyclic issue but then got this one in trying to minimize. So let's start with this import issue.
Looks like it's having trouble to transitively import files.

[lefou]

@joan38 I really love how you provide reproducers. Reminds me of my early Linux from Scratch days.