dev-lang/mujs currently is not multilib, it installs into a hardcoded $prefix/lib and doesn't support shared lib. I'm attaching a patch (for shared support) and ebuild diff which implements these features/fixes.
Created attachment 457002 [details, diff] Implement shared library build
Created attachment 457004 [details, diff] Patch for mujs ebuild implementing multilib and shared/static build
Created attachment 457006 [details, diff] Implement shared library build Fixed a couple of issues in the shared patch
Blocks: bug #506276
This has been fixed a while ago, with the 1.0.1-r1 ebuild. Closing.