[wasm-pic] Explicitly pass asyncify-ignore-imports for non-pic builds

`configure.ac` had been passing `--pass-arg=asyncify-ignore-imports` to
wasm-opt by default, but we cannot use it for dynamic linking builds
because dynamic library can call Ruby's asyncified functions, so we cannot
assume that all imported dynamically linked functions do not change asyncify
state.
Therefore `configure.ac` removed the default `--pass-arg=asyncify-ignore-imports`.
We can still use it for non-pic builds, so we explicitly pass it for
non-pic builds.

Author: kateinoigakukun

lib/ruby_wasm/packager/core.rb

@@ -209,7 +209,9 @@ def derive_build
       # script of Ruby.
       if @packager.full_build_options[:target] != "wasm32-unknown-emscripten"
         build.crossruby.debugflags = %w[-g]
-        build.crossruby.wasmoptflags = %w[-O3 -g]
+        # We assume that imported functions provided through WASI will not change
+        # asyncify state, so we ignore them.
+        build.crossruby.wasmoptflags = %w[-O3 -g --pass-arg=asyncify-ignore-imports]
         build.crossruby.ldflags = %w[
           -Xlinker
           --stack-first