Key wasi-sysroot build flags on the toolchain instead of the target triple

lib/ruby_wasm/build/product/crossruby.rb

@@ -344,8 +344,7 @@ def configure_args(build_triple, toolchain)
       # target-side wasm dump_ast while generating .rbinc files.
       args << %Q(--with-dump-ast=#{dump_ast_path})
 
-      case target
-      when /^wasm32-unknown-wasi/
+      if @toolchain.wasi_sysroot?
         xldflags << @wasi_vfs.lib_wasi_vfs_a if @wasi_vfs
         # TODO: Find a way to force cast or update API
         # @type var wasi_sdk_path: untyped
@@ -363,14 +362,17 @@ def configure_args(build_triple, toolchain)
         # it broke Kernel#require on @bjorn3/browser_wasi_shim setup for some
         # reason. So we disable it for now.
         args << %Q(ac_cv_func_realpath=no)
+      end
+
+      case target
       when "wasm32-unknown-emscripten"
         ldflags.concat(%w[-s MODULARIZE=1])
         env_emcc_ldflags = ENV["RUBY_WASM_EMCC_LDFLAGS"] || ""
         unless env_emcc_ldflags.empty?
           ldflags << env_emcc_ldflags
         end
       else
-        raise "unknown target: #{target}"
+        raise "unknown target: #{target}" unless @toolchain.wasi_sysroot?
       end
 
       args.concat(self.tools_args)

lib/ruby_wasm/build/product/openssl.rb

@@ -42,7 +42,7 @@ def configure_args
         --libdir=lib
         -Wl,--allow-undefined
       ]
-      if @target.triple.start_with?("wasm32-unknown-wasi")
+      if @toolchain.wasi_sysroot?
         args.concat %w[
                       -D_WASI_EMULATED_SIGNAL
                       -D_WASI_EMULATED_PROCESS_CLOCKS

lib/ruby_wasm/build/toolchain.rb

@@ -8,6 +8,12 @@ def initialize
       @tools = {}
     end
 
+    # If this toolchain compiles against wasi-libc, it needs
+    # wasi-libc's emulation feature flags.
+    def wasi_sysroot?
+      false
+    end
+
     def find_tool(name)
       raise "not implemented"
     end
@@ -90,6 +96,10 @@ def initialize(
       @name = "wasi-sdk"
     end
 
+    def wasi_sysroot?
+      true
+    end
+
     def find_tool(name)
       if !File.exist?(@tools[name]) && !ENV["WASI_SDK_PATH"].nil?
         raise "missing tool '#{name}' at #{@tools[name]}"

sig/ruby_wasm/build.rbs

@@ -251,6 +251,7 @@ module RubyWasm
     def ar: -> String
 
     def install: (_CommandExecutor executor) -> void
+    def wasi_sysroot?: -> bool
   end
 
   class WASISDK < Toolchain
@@ -268,6 +269,7 @@ module RubyWasm
     def download_url: () -> String
     def install_wasi_sdk: (_CommandExecutor executor) -> void
     def install: (_CommandExecutor executor) -> void
+    def wasi_sysroot?: -> bool
   end
 
   class Binaryen

test/toolchain_predicate_test.rb

@@ -0,0 +1,17 @@
+require "test-unit"
+require_relative "../lib/ruby_wasm/build/toolchain"
+# require "bundler"
+
+class ToolchainPredicateTest < Test::Unit::TestCase
+  def test_base_toolchain_is_not_wasi_sysroot
+    assert_equal false, Class.new(RubyWasm::Toolchain).allocate.wasi_sysroot?
+  end
+
+  def test_wasi_sdk_is_wasi_sysroot
+    assert_equal true, Class.new(RubyWasm::WASISDK).allocate.wasi_sysroot?
+  end
+
+  def test_emscripten_is_not_wasi_sysroot
+    assert_equal false, Class.new(RubyWasm::Emscripten).allocate.wasi_sysroot?
+  end
+end