[scripts] use RUBY_PLATFORM instead of RbConfig to check platform details for Javy installation

ext/javy/javy.rb

@@ -1,4 +1,3 @@
-require "rbconfig"
 require "open-uri"
 require "zlib"
 require "open3"
@@ -162,17 +161,17 @@ def validate_sha!(source)
     end
   end
 
-  Platform = Struct.new(:ruby_config) do
-    def initialize(ruby_config = RbConfig::CONFIG)
-      super(ruby_config)
+  Platform = Struct.new(:ruby_platform) do
+    def initialize(ruby_platform = RUBY_PLATFORM)
+      super(ruby_platform)
     end
 
     def to_s
       format("%{cpu}-%{os}", cpu: cpu, os: os)
     end
 
     def os
-      case ruby_config.fetch("host_os")
+      case ruby_platform
       when /linux/
         "linux"
       when /darwin/
@@ -183,10 +182,10 @@ def os
     end
 
     def cpu
-      case ruby_config.fetch("host_cpu")
-      when "x64", "x86_64"
+      case ruby_platform
+      when /x64/, /x86_64/
         "x86_64"
-      when "arm"
+      when /arm/
         "arm"
       else
         raise InstallationError.cpu_unsupported

test/ext/javy/javy_test.rb

@@ -154,6 +154,12 @@ def test_recognizes_mac_os_arm
       assert_equal "javy", platform.format_executable_path("javy")
     end
 
+    def test_recognizes_underlying_cpu_in_universal_distributions
+      platform = Javy::Platform.new(PlatformHelper.macos_universal_config)
+      assert_equal "arm-macos", platform.to_s
+      assert_equal "javy", platform.format_executable_path("javy")
+    end
+
     def test_recognizes_windows
       platform = Javy::Platform.new(PlatformHelper.windows_config)
       assert_equal "x86_64-windows", platform.to_s
@@ -220,6 +226,10 @@ def self.macos_arm_config
       ruby_config(os: "darwin20.3.0", cpu: "arm")
     end
 
+    def self.macos_universal_config
+      ruby_config(os: "darwin20.3.0", cpu: "universal.arm64")
+    end
+
     def self.windows_config
       ruby_config(os: "mingw32", cpu: "x64")
     end
@@ -229,10 +239,7 @@ def self.windows_32_bit_config
     end
 
     def self.ruby_config(os:, cpu:)
-      {
-        "host_os" => os,
-        "host_cpu" => cpu,
-      }
+      "#{cpu}-#{os}"
     end
   end
 end