internal/rosa: create /bin symlinks via helper

This centralises the workaround for surprisingly common buggy scripts with nonstandard hardcoded paths.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/state.go

@@ -1004,15 +1004,17 @@ func (ctx *evalContext) pf(
 		k("block"):       &meta.Blocked,
 		k("latest"):      &meta.latest,
 
-		k("writable"):    &attr.Writable,
-		k("chmod"):       &attr.Chmod,
-		k("enterSource"): &attr.EnterSource,
-		k("env"):         &attr.Env,
-		k("early"):       &attr.ScriptEarly,
-		k("patches"):     &patches,
-		k("files"):       &files,
-		k("exclusive"):   &excl,
-		k("toyboxEarly"): &early,
+		k("writable"):       &attr.Writable,
+		k("chmod"):          &attr.Chmod,
+		k("enterSource"):    &attr.EnterSource,
+		k("env"):            &attr.Env,
+		k("early"):          &attr.ScriptEarly,
+		k("bin"):            &attr.Bin,
+		k("populateUsrBin"): &attr.PopulateUsrBin,
+		k("patches"):        &patches,
+		k("files"):          &files,
+		k("exclusive"):      &excl,
+		k("toyboxEarly"):    &early,
 
 		k("checksum"): &kc,
 		k("output"):   &output,