Parse the extconf instead of running it:

Gemfile.lock

@@ -2,13 +2,15 @@ PATH
   remote: .
   specs:
     easy_compile (0.1.1)
+      prism
       rake-compiler
       thor
 
 GEM
   remote: https://rubygems.org/
   specs:
     minitest (5.25.5)
+    prism (1.6.0)
     rake (13.3.0)
     rake-compiler (1.3.0)
       rake

easy_compile.gemspec

@@ -25,4 +25,5 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "rake-compiler"
   spec.add_dependency "thor"
+  spec.add_dependency "prism"
 end

lib/easy_compile/cli.rb

@@ -134,7 +134,8 @@ def run_rake_tasks!(*tasks)
       rake_specs = Gem.loaded_specs["rake"]
       rake_executable = rake_specs.bin_file("rake")
       rake_path = rake_specs.full_require_paths
-      load_paths = (rake_compiler_path + rake_path).join(File::PATH_SEPARATOR)
+      prism_path = Gem.loaded_specs["prism"].full_require_paths
+      load_paths = (rake_compiler_path + rake_path + prism_path).join(File::PATH_SEPARATOR)
 
       system({ "RUBYLIB" => load_paths }, "bundle exec #{RbConfig.ruby} #{rake_executable} #{all_tasks} -R#{rakelibdir}", exception: true)
     end

lib/easy_compile/compilation_tasks.rb

@@ -3,11 +3,11 @@
 require "bundler"
 require "rubygems/package_task"
 require "rake/extensiontask"
+require_relative "create_makefile_finder"
 
 module EasyCompile
   class CompilationTasks
     attr_reader :gemspec, :native, :create_packaging_task, :extension_task
-    attr_accessor :binary_name
 
     def initialize(create_packaging_task = false, gemspec = nil)
       @gemspec  = Bundler.load_gemspec(gemspec || find_gemspec)
@@ -17,10 +17,9 @@ def initialize(create_packaging_task = false, gemspec = nil)
     end
 
     def setup
-      with_mkmf_monkey_patch do
-        gemspec.extensions.each do |path|
-          define_task(path)
-        end
+      gemspec.extensions.each do |path|
+        binary_name = parse_extconf(path)
+        define_task(path, binary_name)
       end
 
       setup_packaging if create_packaging_task
@@ -52,46 +51,21 @@ def setup_packaging
       end
     end
 
-    def with_mkmf_monkey_patch
-      require "mkmf"
-
-      instance = self
-
-      previous_create_makefile = method(:create_makefile)
-      Object.define_method(:create_makefile) do |name, *args|
-        instance.binary_name = name
-        previous_create_makefile.call(name, *args)
-      end
-
-      Object.define_method(:create_rust_makefile) do |name, *args|
-        instance.binary_name = name
-      end
-
-      yield
-    ensure
-      Object.remove_method(:create_makefile)
-      Object.remove_method(:create_rust_makefile)
-    end
-
-    def define_task(path)
-      require File.expand_path(path)
-
+    def define_task(path, binary_name)
       @extension_task = Rake::ExtensionTask.new do |ext|
         ext.name = File.basename(binary_name)
         ext.config_script = File.basename(path)
         ext.ext_dir = File.dirname(path)
-        ext.lib_dir = binary_lib_dir if binary_lib_dir
+        ext.lib_dir = binary_lib_dir(binary_name) if binary_lib_dir(binary_name)
         ext.gem_spec = gemspec
         ext.cross_platform = normalized_platform
         ext.cross_compile = true
       end
 
       disable_shared unless Gem.win_platform?
-    ensure
-      self.binary_name = nil
     end
 
-    def binary_lib_dir
+    def binary_lib_dir(binary_name)
       dir = File.dirname(binary_name)
       return if dir == "."
 
@@ -137,5 +111,12 @@ def verify_gemspec!
         This tool can't be used on pure Ruby gems.
       EOM
     end
+
+    def parse_extconf(path)
+      visitor = CreateMakefileFinder.new
+      Prism.parse_file(path).value.accept(visitor)
+
+      visitor.binary_name
+    end
   end
 end

lib/easy_compile/create_makefile_finder.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require "prism"
+
+module EasyCompile
+  class CreateMakefileFinder < Prism::Visitor
+    attr_reader :binary_name
+
+    def visit_call_node(node)
+      super
+      looking_for = [:create_makefile, :create_rust_makefile]
+      return unless looking_for.include?(node.name)
+
+      @binary_name = node.arguments.child_nodes.first.content
+    end
+  end
+end