update how to build

README.md

@@ -37,6 +37,14 @@ Segmentation Network: FCN PSPNet ...
 
 **[how to build ncnn library](https://github.com/Tencent/ncnn/wiki/how-to-build) on Linux / Windows / Raspberry Pi3 / Android  / iOS**
 
+* [Build for Linux x86](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-linux-x86)
+* [Build for Windows x64 using VS2017](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-windows-x64-using-visual-studio-community-2017)
+* [Build for MacOSX](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-macosx)
+* [Build for Raspberry Pi 3](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-raspberry-pi-3)
+* [Build for Android](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-android)
+* [Build for iOS on MacOSX with xcode](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-ios-on-macosx-with-xcode)
+* [Build for iOS on Linux with cctools-port](https://github.com/Tencent/ncnn/wiki/how-to-build#build-for-ios-on-linux-with-cctools-port)
+
 **[how to use ncnn with alexnet](https://github.com/Tencent/ncnn/wiki/how-to-use-ncnn-with-alexnet) with detailed steps, recommended for beginners :)**
 
 **[ncnn 组件使用指北 alexnet](https://github.com/Tencent/ncnn/wiki/ncnn-%E7%BB%84%E4%BB%B6%E4%BD%BF%E7%94%A8%E6%8C%87%E5%8C%97-alexnet) 附带详细步骤，新人强烈推荐 :)**