Pass the command line to cl.exe through a file (crystal-lang#9062)

This is necessary because large projects (like the Crystal compiler) surpass the maximal size for the command line when linking the numerous object files.

This commit also makes Crystal actually be able to run the linker subprocess, as it removes the unsupported combination of `args` and `shell: true`.

src/compiler/crystal/compiler.cr

@@ -22,7 +22,7 @@ module Crystal
   # optionally generates an executable.
   class Compiler
     CC = ENV["CC"]? || "cc"
-    CL = "cl"
+    CL = "cl.exe"
 
     # A source to the compiler: its filename and source code.
     record Source,
@@ -314,22 +314,35 @@ module Crystal
 
       target_machine.emit_obj_to_file llvm_mod, object_name
 
-      stdout.puts linker_command(program, object_name, output_filename, nil)
+      print_command(*linker_command(program, [object_name], output_filename, nil))
     end
 
-    private def linker_command(program : Program, object_name, output_filename, output_dir)
-      if program.has_flag? "windows"
-        if object_name
-          object_name = %("#{object_name}")
-        else
-          object_name = %(%*)
-        end
+    private def print_command(command, args)
+      stdout.puts command.sub(%("${@}"), args && args.join(" "))
+    end
 
+    private def linker_command(program : Program, object_names, output_filename, output_dir)
+      if program.has_flag? "windows"
         if link_flags = @link_flags.presence
           link_flags = "/link #{link_flags}"
         end
 
-        %(#{CL} #{object_name} "/Fe#{output_filename}" #{program.lib_flags} #{link_flags})
+        args = %(#{object_names.join(" ")} "/Fe#{output_filename}" #{program.lib_flags} #{link_flags})
+        cmd = "#{CL} #{args}"
+
+        if cmd.to_utf16.size > 32000
+          # The command line would be too big, pass the args through a UTF-16-encoded file instead.
+          # TODO: Use a proper way to write encoded text to a file when that's supported.
+          # The first character is the BOM; it will be converted in the same endianness as the rest.
+          args_16 = "\ufeff#{args}".to_utf16
+          args_bytes = args_16.to_unsafe.as(UInt8*).to_slice(args_16.bytesize)
+
+          args_filename = "#{output_dir}/linker_args.txt"
+          File.write(args_filename, args_bytes)
+          cmd = "#{CL} @#{args_filename}"
+        end
+
+        {cmd, nil}
       else
         if thin_lto
           clang = ENV["CLANG"]? || "clang"
@@ -344,17 +357,11 @@ module Crystal
           cc = CC
         end
 
-        if object_name
-          object_name = %('#{object_name}')
-        else
-          object_name = %("${@}")
-        end
-
         link_flags = @link_flags || ""
         link_flags += " -rdynamic"
         link_flags += " -static" if static?
 
-        %(#{cc} #{object_name} -o '#{output_filename}' #{link_flags} #{program.lib_flags})
+        { %(#{cc} "${@}" -o '#{output_filename}' #{link_flags} #{program.lib_flags}), object_names }
       end
     end
 
@@ -389,9 +396,9 @@ module Crystal
 
       @progress_tracker.stage("Codegen (linking)") do
         Dir.cd(output_dir) do
-          linker_command = linker_command(program, nil, output_filename, output_dir)
+          linker_command = linker_command(program, object_names, output_filename, output_dir)
 
-          process_wrapper(linker_command, object_names) do |command, args|
+          process_wrapper(*linker_command) do |command, args|
             Process.run(command, args, shell: true,
               input: Process::Redirect::Close, output: Process::Redirect::Inherit, error: Process::Redirect::Pipe) do |process|
               process.error.each_line(chomp: false) do |line|
@@ -563,15 +570,8 @@ module Crystal
       end
     end
 
-    private def system(command, args = nil)
-      process_wrapper(command, args) do
-        ::system(command, args)
-        $?
-      end
-    end
-
     private def process_wrapper(command, args = nil)
-      stdout.puts "#{command} #{args.join " "}" if verbose?
+      print_command(command, args) if verbose?
 
       status = yield command, args