dev-python/pypy-bin: Fix mtimes between generated and source files

Ensure to preserve file mtimes while copying them from the source tree
to the installation image. This ensures that the generated files
are newer than source files, and that PyPy does not attempt to rewrite
them at runtime.

dev-python/pypy-bin/pypy-bin-5.9.0-r2.ebuild

@@ -171,6 +171,8 @@ src_install() {
 	doexe pypy-c libpypy-c.so
 	pax-mark m "${ED%/}${dest}/pypy-c" "${ED%/}${dest}/libpypy-c.so"
 	insinto "${dest}"
+	# preserve mtimes to avoid obsoleting caches
+	insopts -p
 	doins -r include lib_pypy lib-python
 	dosym ../$(get_libdir)/pypy/pypy-c /usr/bin/pypy
 	dodoc README.rst