High Sierra環境だと、macportsでosxfuse(sshfs)がインストールできない問題

macportsでsshfsをインストールしようとしたら、突然出来なくなった。
のでそんな時の対処法。

参考URL
\#54939 (osxfuse @3.7.1: Library not loaded: @rpath/libclang.dylib (LoadError)) – MacPorts https://trac.macports.org/ticket/54939#no1

###エラー
osxfuseがあんなことやこんなことでbuild出来ないと言われる。

```:terminal
$ sudo port install sshfs
Password:
--->  Computing dependencies for sshfs
The following dependencies will be installed:  osxfuse
Continue? [Y/n]: Y
--->  Fetching archive for osxfuse
--->  Attempting to fetch osxfuse-3.7.1_0.darwin_17.x86_64.tbz2 from https://packages.macports.org/osxfuse
--->  Attempting to fetch osxfuse-3.7.1_0.darwin_17.x86_64.tbz2 from http://fco.it.packages.macports.org/mirrors/macports-packages/osxfuse
--->  Attempting to fetch osxfuse-3.7.1_0.darwin_17.x86_64.tbz2 from http://jnb.za.packages.macports.org/packages/osxfuse
--->  Fetching distfiles for osxfuse
--->  Verifying checksums for osxfuse
--->  Extracting osxfuse
--->  Configuring osxfuse
--->  Building osxfuse
Error: Failed to build osxfuse: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_www.macports.org_files_ports_fuse_osxfuse/osxfuse/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port sshfs failed
```

ログを見ろと出るのでログを見ると

```:/opt/local/var/macports/logs/_opt_local_var_macports_sources_www.macports.org_files_ports_fuse_osxfuse/osxfuse/main.log
:info:build /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': dlopen(/System/Library/BridgeSupport/ruby-2.3/bridgesupportparser.bundle, 9): Library not loaded: @rpath/libclang.dylib (LoadError)
:info:build   Referenced from: /System/Library/BridgeSupport/ruby-2.3/bridgesupportparser.bundle
:info:build   Reason: image not found - /System/Library/BridgeSupport/ruby-2.3/bridgesupportparser.bundle
```

端的に言えばHighSierraではそのままだと無理のよう。

###対処法

####1.xcodeのtoolchainを変更する
defaultのtoolchainsに、High Sierra（OSX10.13)のtoolchainをリンクする。

```:terminal
$ cd /Applications/Xcode.app/Contents/Developer/Toolchains
$ sudo ln -s XcodeDefault.xctoolchain OSX10.13.xctoolchain
```

####2.sshfsをインストール
sshfsを通常コマンドでインストールする。

```:terminal
$ sudo port install sshfs
--->  Computing dependencies for sshfs
The following dependencies will be installed:  osxfuse
Continue? [Y/n]: Y
--->  Building osxfuse
--->  Staging osxfuse into destroot
Warning: osxfuse installs files outside the common directory structure.
--->  Installing osxfuse @3.7.1_0
--->  Activating osxfuse @3.7.1_0
--->  Cleaning osxfuse
--->  Fetching archive for sshfs
--->  Attempting to fetch sshfs-2.10_0.darwin_17.x86_64.tbz2 from https://packages.macports.org/sshfs
--->  Attempting to fetch sshfs-2.10_0.darwin_17.x86_64.tbz2 from http://fco.it.packages.macports.org/mirrors/macports-packages/sshfs
--->  Attempting to fetch sshfs-2.10_0.darwin_17.x86_64.tbz2 from http://jnb.za.packages.macports.org/packages/sshfs
--->  Fetching distfiles for sshfs
--->  Attempting to fetch sshfs-2.10.tar.gz from https://github.com/libfuse/sshfs/tarball/sshfs-2.10
--->  Verifying checksums for sshfs                                                          
--->  Extracting sshfs
--->  Applying patches to sshfs
--->  Configuring sshfs
--->  Building sshfs
--->  Staging sshfs into destroot
--->  Installing sshfs @2.10_0
--->  Activating sshfs @2.10_0
--->  Cleaning sshfs
--->  Updating database of binaries
--->  Scanning binaries for linking errors
--->  No broken files found.
--->  Some of the ports you installed have notes:
  osxfuse has the following notes:
    When upgrading, unmount all FUSE filesystems and then unload the kernel extension.
    Unloading can be done via: sudo kextunload -b com.github.osxfuse.filesystems.osxfuse
    Alternatively (or if this fails), just reboot your computer now.
```

とりあえずこれで動くようにはなったのだが、toolchainsを換えているので、何か変なこと起こったりしないんだろうかと思ったり、思わなかったり。

```:terminal
$ sshfs
missing host
see `sshfs -h' for usage
```