Manually compile libargon2 instead of using make

As the libargon2 Makefile shells out to `uname -s` and `uname -m`, it
passes invalid linker flags when cross-compiling (as we're compiling for
one OS but on a host machine that might use another).

Instead of bending over backwards to work around this, abandon using
their Makefile altogether and instead reproduce the specific logic we
need, i.e.

1. Compile each of the core object files in a position independent way
2. Create a static archive of those object files

This way, we only build what we need and hopefully in a way that is a
static library on as many platforms as possible.

README.md

@@ -26,6 +26,7 @@ Argon2::Password.create("opensesame") == "notopensesame" #=> false
     * [Native gems](#native-gems)
     * [Verifying the gems](#verifying-the-gems)
     * [Installing the `ruby` platform gem](#installing-the-ruby-platform-gem)
+* [Thanks](#thanks)
 * [Contact](#contact)
 * [License](#license)
     * [Dependencies](#dependencies)
@@ -215,6 +216,11 @@ You will need a full compiler toolchain for compiling Ruby C extensions (see
 Toolchain"](https://nokogiri.org/tutorials/installing_nokogiri.html#appendix-a-the-compiler-toolchain))
 plus the toolchain required for compiling the vendored version of Argon2.
 
+## Thanks
+
+* Thanks to [Mike Dalessio](https://github.com/flavorjones) for his advice and
+  work on [MiniPortile](https://github.com/flavorjones/mini_portile)
+
 ## Contact
 
 All issues and suggestions should go to [GitHub

ext/argon2id/extconf.rb

@@ -4,8 +4,6 @@
 
 require_relative "recipe"
 
-# Configure cross-compiler
-RbConfig::CONFIG["CC"] = RbConfig::MAKEFILE_CONFIG["CC"] = ENV["CC"] if ENV["CC"]
 $CFLAGS << " -Wextra"
 
 have_header("stdint.h")

ext/argon2id/recipe.rb

@@ -17,32 +17,46 @@ def configured?
     end
 
     def compile
-      cflags = [ENV["CFLAGS"], "-fPIC"].compact.join(" ")
-      env = {
-        "PREFIX" => File.expand_path(port_path),
-        "LIBRARY_REL" => "lib",
-        "CC" => gcc_cmd,
-        "CFLAGS" => cflags
-      }
+      # libargon2's Makefile shells out to uname to determine the host platform
+      # which doesn't work when cross-compiling. Instead, we manually compile
+      # the necessary source files and generate only the static library in the
+      # hopes that it is compatible across the most platforms.
+      cflags = [ENV["CFLAGS"], "-std=c89", "-O3", "-Wall", "-g", "-Iinclude", "-Isrc", "-fPIC", "-pthread"].compact.join(" ")
+      objs = %w[argon2 core blake2/blake2b thread encoding ref]
+      objs.each do |obj|
+        execute("compile-#{File.basename(obj)}", "#{gcc_cmd} #{cflags} -c -o src/#{obj}.o src/#{obj}.c")
+      end
+
+      ar_cmd = ENV["AR"] || "ar"
+      arflags = ENV["ARFLAGS"] || "rcs"
+
+      # Thanks to @flavorjones for this, see
+      # https://github.com/sparklemotion/nokogiri/blob/e05b9949b794ca94b37a90f2fb2555d99a37daa5/ext/nokogiri/extconf.rb#L1074-L1127
       if enable_config("cross-build")
-        if host.include?("darwin")
-          env["AR"] = "#{host}-libtool"
-          env["ARFLAGS"] = "-o"
+        case host
+        when /darwin/
+          ar_cmd = "#{host}-libtool"
+          arflags = "-o"
+        when "i686-redhat-linux"
+          ar_cmd = "i686-redhat-linux-gnu-ar"
+        when "x86_64-redhat-linux"
+          ar_cmd = "x86_64-redhat-linux-gnu-ar"
         else
-          env["AR"] = "#{host}-ar"
+          ar_cmd = "#{host}-ar"
         end
       end
 
-      execute("compile", make_cmd, env: env)
+      execute("archive", "#{ar_cmd} #{arflags} libargon2.a #{objs.map { |obj| "src/#{obj}.o" }.join(" ")}")
     end
 
     def install
       return if installed?
 
-      execute("install", "#{make_cmd} install", env: {
-        "PREFIX" => File.expand_path(port_path),
-        "LIBRARY_REL" => "lib"
-      })
+      lib_dir = File.join(port_path, "lib")
+      include_dir = File.join(port_path, "include")
+      FileUtils.mkdir_p([lib_dir, include_dir])
+      FileUtils.cp(File.join(work_path, "libargon2.a"), lib_dir)
+      FileUtils.cp(File.join(work_path, "include", "argon2.h"), include_dir)
     end
   end