Properly building the gem file under mingw using rake-compiler-dock.

src/ruby/ext/grpc/extconf.rb

@@ -54,9 +54,6 @@ LIB_DIRS = [
   LIBDIR
 ]
 
-fail 'libdl not found' unless have_library('dl', 'dlopen')
-fail 'zlib not found' unless have_library('z', 'inflate')
-
 grpc_root = File.expand_path(File.join(File.dirname(__FILE__), '../../../..'))
 
 grpc_config = ENV['GRPC_CONFIG'] || 'opt'
@@ -64,12 +61,37 @@ grpc_config = ENV['GRPC_CONFIG'] || 'opt'
 if ENV.key?('GRPC_LIB_DIR')
   grpc_lib_dir = File.join(grpc_root, ENV['GRPC_LIB_DIR'])
 else
-  grpc_lib_dir = File.join(File.join(grpc_root, 'libs'), grpc_config)
+  grpc_lib_dir = File.join(grpc_root, 'libs', grpc_config)
 end
 
 unless File.exist?(File.join(grpc_lib_dir, 'libgrpc.a'))
-  print "Building internal gRPC\n"
-  system("make -C #{grpc_root} static_c CONFIG=#{grpc_config}")
+  for var in %w( CC AR ) do
+    ENV[var] = RbConfig::CONFIG[var]
+  end
+
+  ENV['LD'] = ENV['CC']
+
+  if RUBY_PLATFORM =~ /mingw|mswin/
+    ENV['SYSTEM'] = 'MINGW32'
+  end
+
+  ENV['EMBED_OPENSSL'] = 'true'
+  ENV['EMBED_ZLIB'] = 'true'
+
+  grpc_cppflags = ''
+  grpc_cppflags << ' -D_WIN32_WINNT=0x600 '
+  grpc_cppflags << ' -DUNICODE '
+  grpc_cppflags << ' -D_UNICODE '
+
+  ENV['CPPFLAGS'] = grpc_cppflags
+
+  output_dir = File.expand_path(RbConfig::CONFIG['topdir'])
+  grpc_lib_dir = File.join(output_dir, 'libs', grpc_config)
+  ENV['BUILDDIR'] = output_dir
+
+  puts 'Building internal gRPC into ' + grpc_lib_dir
+  system("make -j -C #{grpc_root} static_c CONFIG=#{grpc_config}")
+  exit 1 unless $? == 0
 end
 
 $CFLAGS << ' -I' + File.join(grpc_root, 'include')
@@ -85,8 +107,25 @@ $CFLAGS << ' -Wall '
 $CFLAGS << ' -Wextra '
 $CFLAGS << ' -pedantic '
 $CFLAGS << ' -Werror '
+$CFLAGS << ' -Wno-format '
+
+subdir = RUBY_VERSION.sub(/\.\d$/,'')
+output = File.join('grpc', 'grpc')
+puts 'Generating Makefile for ' + output
+create_makefile(output)
+
+strip_tool = RbConfig::CONFIG['STRIP']
+
+File.open('Makefile.new', 'w') do |o|
+  o.puts 'hijack: all strip'
+  o.puts
+  File.foreach('Makefile') do |i|
+    o.puts i
+  end
+  o.puts
+  o.puts 'strip:'
+  o.puts "\t$(ECHO) Stripping $(DLLIB)"
+  o.puts "\t$(Q) #{strip_tool} $(DLLIB)"
+end
 
-$LDFLAGS << ' -lssl '
-$LDFLAGS << ' -lcrypto '
-
-create_makefile('grpc/grpc')
+File.rename('Makefile.new', 'Makefile')