remove Method.roots with --strip-ir (#54676)

This "roots" list is now only used for references to values in IR, and
so is really part of the IR representation and can be removed by
--strip-ir (and is also a bit mis-named).

src/codegen.cpp

@@ -3167,7 +3167,7 @@ static jl_value_t *jl_ensure_rooted(jl_codectx_t &ctx, jl_value_t *val)
  if (jl_is_globally_rooted(val))
  return val;
  jl_method_t *m = ctx.linfo->def.method;
- if (jl_is_method(m)) {
+ if (!jl_options.strip_ir && jl_is_method(m)) {
  // the method might have a root for this already; use it if so
  JL_LOCK(&m->writelock);
  if (m->roots) {

src/staticdata.c

@@ -2437,6 +2437,7 @@ static int strip_all_codeinfos__(jl_typemap_entry_t *def, void *_env)
  }
  if (should_strip_ir) {
  record_field_change(&m->source, jl_nothing);
+ record_field_change((jl_value_t**)&m->roots, NULL);
  stripped_ir = 1;
  }
  }