build: Add experimental PIC support for WASI target

lib/ruby_wasm/build/product/crossruby.rb

@@ -286,7 +286,7 @@ def configure_args(build_triple, toolchain)
       xldflags = @xldflags.dup
 
       args = self.system_triplet_args + ["--build", build_triple]
-      args << "--with-static-linked-ext"
+      args << "--with-static-linked-ext" unless @params.target.pic?
       args << %Q(--with-ext=#{default_exts})
       args << %Q(--with-libyaml-dir=#{@libyaml.install_root})
       args << %Q(--with-zlib-dir=#{@zlib.install_root})

lib/ruby_wasm/build/product/libyaml.rb

@@ -58,6 +58,8 @@ def build(executor)
                       "#{product_build_dir}/config/config.sub",
                       "https://cdn.jsdelivr.net/gh/gcc-mirror/gcc@master/config.sub"
 
+      configure_args = self.configure_args.dup
+      configure_args << "CFLAGS=-fPIC" if target.pic?
       executor.system "./configure", *configure_args, chdir: product_build_dir
       executor.system "make",
                       "install",

lib/ruby_wasm/build/product/openssl.rb

@@ -52,6 +52,11 @@ def configure_args
                       -DHAVE_FORK=0
                     ]
       end
+
+      if @target.pic?
+        args << "-fPIC"
+      end
+
       args + tools_args
     end
 

lib/ruby_wasm/build/product/zlib.rb

@@ -54,6 +54,8 @@ def build(executor)
                       product_build_dir,
                       "--strip-components=1"
 
+      configure_args = self.configure_args.dup
+      configure_args << "CFLAGS=-fPIC" if target.pic?
       executor.system "env",
                       *configure_args,
                       "./configure",

lib/ruby_wasm/packager.rb

@@ -35,7 +35,7 @@ def package(executor, dest_dir, options)
     fs.remove_non_runtime_files(executor)
     fs.remove_stdlib(executor) unless options[:stdlib]
 
-    if full_build_options[:target] == "wasm32-unknown-wasi"
+    if full_build_options[:target] == "wasm32-unknown-wasi" && !support_dynamic_linking?
       # wasi-vfs supports only WASI target
       wasi_vfs = RubyWasmExt::WasiVfs.new
       wasi_vfs.map_dir("/bundle", fs.bundle_dir)

lib/ruby_wasm/packager/core.rb

@@ -61,6 +61,100 @@ def artifact
   end
 
   class DynamicLinking < BuildStrategy
+    def build(executor, options)
+      build = derive_build
+      force_rebuild =
+        options[:remake] || options[:clean] || options[:reconfigure]
+      if File.exist?(build.crossruby.artifact) && !force_rebuild
+        return build.crossruby.artifact
+      end
+      build.crossruby.clean(executor) if options[:clean]
+
+      do_build =
+        proc do
+          build.crossruby.build(
+            executor,
+            remake: options[:remake],
+            reconfigure: options[:reconfigure]
+          )
+        end
+
+      __skip__ =
+        if defined?(Bundler)
+          Bundler.with_unbundled_env(&do_build)
+        else
+          do_build.call
+        end
+      build.crossruby.artifact
+    end
+
+    def build_exts(build)
+      specs_with_extensions.flat_map do |spec, exts|
+        exts.map do |ext|
+          ext_feature = File.dirname(ext) # e.g. "ext/cgi/escape"
+          ext_srcdir = File.join(spec.full_gem_path, ext_feature)
+          ext_relative_path = File.join(spec.full_name, ext_feature)
+          RubyWasm::CrossRubyExtProduct.new(
+            ext_srcdir,
+            build.toolchain,
+            ext_relative_path: ext_relative_path
+          )
+        end
+      end
+    end
+
+    def cache_key(digest)
+      derive_build.cache_key(digest)
+    end
+
+    def artifact
+      derive_build.crossruby.artifact
+    end
+
+    def target
+      RubyWasm::Target.new(@packager.full_build_options[:target], pic: true)
+    end
+
+    def derive_build
+      return @build if @build
+      __skip__ =
+        build ||= RubyWasm::Build.new(
+          name, **@packager.full_build_options,
+          target: target,
+          # NOTE: We don't need linking libwasi_vfs because we use wasi-virt instead.
+          wasi_vfs: nil
+        )
+      build.crossruby.cflags = %w[-fPIC -fvisibility=default]
+      if @packager.full_build_options[:target] != "wasm32-unknown-emscripten"
+        build.crossruby.debugflags = %w[-g]
+        build.crossruby.wasmoptflags = %w[-O3 -g]
+        build.crossruby.ldflags = %w[
+          -Xlinker
+          --stack-first
+          -Xlinker
+          -z
+          -Xlinker
+          stack-size=16777216
+        ]
+        build.crossruby.xldflags = %w[
+          -Xlinker -shared
+          -Xlinker --export-dynamic
+          -Xlinker --export-all
+          -Xlinker --experimental-pic
+          -Xlinker -export-if-defined=__main_argc_argv
+        ]
+      end
+      @build = build
+      build
+    end
+
+    def name
+      require "digest"
+      options = @packager.full_build_options
+      src_channel = options[:src][:name]
+      target_triplet = options[:target]
+      "ruby-#{src_channel}-#{target_triplet}-pic#{options[:suffix]}"
+    end
   end
 
   class StaticLinking < BuildStrategy
@@ -100,7 +194,7 @@ def artifact
     end
 
     def target
-      RubyWasm::Target.new(@packager.full_build_options[:target], pic: true)
+      RubyWasm::Target.new(@packager.full_build_options[:target])
     end
 
     def derive_build

sig/ruby_wasm/build.rbs

@@ -314,19 +314,9 @@ module RubyWasm
   end
 
   class BuildTask
-    @build_dir: String
-    @rubies_dir: String
-    @openssl: OpenSSLProduct
-
+    @build: Build
     attr_accessor name: String
-    attr_reader source: BuildSource
-    attr_reader target: String
-    attr_reader toolchain: Toolchain
-    attr_reader libyaml: LibYAMLProduct
-    attr_reader zlib: ZlibProduct
-    attr_reader wasi_vfs: WasiVfsProduct
-    attr_reader baseruby: BaseRubyProduct
-    attr_reader crossruby: CrossRubyProduct
+
     def initialize: (String name, target: String, src: untyped, ?toolchain: Toolchain?, ?build_dir: String?, ?rubies_dir: String?, **untyped) -> void
     def hexdigest: -> String
   end

sig/ruby_wasm/packager.rbs

@@ -66,6 +66,9 @@ class RubyWasm::Packager
     end
 
     class DynamicLinking < RubyWasm::Packager::Core::BuildStrategy
+      @build: RubyWasm::Build
+      def derive_build: () -> RubyWasm::Build
+      def name: () -> string
     end
 
     class StaticLinking < RubyWasm::Packager::Core::BuildStrategy