Update installation doc for macOS.

docs/install-on-osx.md

@@ -1,133 +1,46 @@
-# @title Install ruby-oci8 on OS X
+# @title Install ruby-oci8 on macOS
 
-Install ruby-oci8 on OS X
+Install ruby-oci8 on macOS
 =========================
 
-This page explains the way to install ruby-oci8 os OS X.
+**Note: Ruby-oci8 doesn't run on Apple Silicon because Oracle instant client
+for Apple Silicon has not been released yet.**
 
-Look at {file:docs/install-full-client.md}, {file:docs/install-instant-client.md}
-or {file:docs/install-binary-package.md} for other platforms.
-
-Install C compiler
-------------------
-
-You need to install the command line developer tools or the Xcode.
-(The latter includes the former.)
-
-Run `"cc --version"` in a terminal to check whether they are installed.
-
-If the cc version is printed, the tools are installed.
-
-If the follwoing dialog is displayed, click its Install button to
-install the tools.
-You have no need to install the Xcode to compile ruby-oci8.
-It requires command line tools, not an IDE such as the Xcode.
-
-![dialog](osx-install-dev-tools.png)
+Prerequisite
+------------
 
-If `"Agreeing to the Xcode/iOS license requires admin privileges,
-please re-run as root via sudo."` is printed, you need to run
-`"sudo cc --version"`, enter your password, look at the license
-and type `"agree"`.
+* Command line tools for Xcode or Xcode (by executing `xcode-select --install`) or [Xcode]
 
 Install Oracle Instant Client Packages
 --------------------------------------
 
-### Download Oracle Instant Client Packages
-
-Download the following packages from [Oracle Technology Network][]
-
-* Instant Client Package - Basic (`instantclient-basic-macos.x64-12.1.0.2.0.zip`) or Basic Lite (`instantclient-basiclite-macos.x64-12.1.0.2.0.zip`)
-* Instant Client Package - SDK (`instantclient-sdk-macos.x64-12.1.0.2.0.zip`)
-* Instant Client Package - SQL*Plus (`instantclient-sqlplus-macos.x64-12.1.0.2.0.zip`) (optionally) 
-
-### Install Oracle Instant Client Packages via Homebrew
-
-To install `Oracle Instant Client Basic` via [Homebrew][]
-
-* Copy downloaded zip files to `/Library/Caches/Homebrew`
-  (if the environment variable `HOMEBREW_CACHE`
-  is not set and `$HOME/Library/Caches/Homebrew` doesn't exist.)
-
-* Run the followining commands:
-
-        brew tap InstantClientTap/instantclient
-        brew install instantclient-basic
-        brew install instantclient-sdk
-        brew install instantclient-sqlplus # (optionally)
-
-* Set the environment variable `OCI_DIR` while performing the following installation steps
-  if Homebrew is installed outside `/usr/local`.
-
-        export OCI_DIR=$(brew --prefix)/lib
-
-To install `Oracle Instant Client Basic Lite` via [Homebrew][]
-
-* Copy downloaded zip files to `/Library/Caches/Homebrew`
-  (if the environment variable `HOMEBREW_CACHE`
-  is not set and `$HOME/Library/Caches/Homebrew` doesn't exist.)
-
-* Run the followining commands:
-
-        brew tap InstantClientTap/instantclient
-        brew install instantclient-basiclite
-        brew install instantclient-sdk
-        brew install instantclient-sqlplus --with-basiclite # (optionally)
-        
-* Set the environment variable `OCI_DIR` while performing the following installation steps
-  if Homebrew is installed outside `/usr/local`.
-
-        export OCI_DIR=$(brew --prefix)/lib
-
-### Install Oracle Instant Client Manually
-
-If you don't use [Homebrew][], do the following:
-
-Unzip the packages as follows:
-
-    mkdir -p /opt/oracle
-    cd /opt/oracle
-
-Copy downloaded files to /opt/oracle before running the following commands.
-
-    unzip instantclient-basic-macos.x64-12.1.0.2.0.zip
-    unzip instantclient-sdk-macos.x64-12.1.0.2.0.zip
-    unzip instantclient-sqlplus-macos.x64-12.1.0.2.0.zip
-
-Make a symbolic link to link the library.
-
-    cd /opt/oracle/instantclient_12_1
-    ln -s libclntsh.dylib.12.1 libclntsh.dylib
-
-Set the environment variable OCI_DIR while performing the following installation steps.
-
-    export OCI_DIR=/opt/oracle/instantclient_12_1
-
-Installation
-------------
-
-If you get a problem in the following steps, look at {file:docs/report-installation-issue.md}.
-
-### gem package
-
-Run the following command.
+If you have installed [Homebrew], use the following command:
 
-    gem install ruby-oci8
+```shell
+$ brew tap InstantClientTap/instantclient
+$ brew install instantclient-basic   # or instantclient-basiclite
+$ brew install instantclient-sdk
+$ brew install instantclient-sqlplus # (optionally)
+```
 
-### tar.gz package
+Otherwise, look at this [page][OTN] and set the environment variable
+`OCI_DIR` to point the the directory where instant client is installed.
+Ruby-oci8 installation script checks the directory.
 
-#### Download the source code
+```shell
+export OCI_DIR=$HOME/Downloads/instantclient_19_8  # for example
+```
 
-Download the latest tar.gz package from [download page][].
+Install ruby-oci8
+-----------------
 
-#### Run make and install
+Note that `/usr/bin/ruby` isn't available. You need to use [`rbenv`] or so.
 
-    tar xvfz ruby-oci8-VERSION.tar.gz
-    cd ruby-oci8-VERSION
-    make
-    make install
+```shell
+$ gem install ruby-oci8
+```
 
-[download page]: https://bintray.com/kubo/generic/ruby-oci8
 [Homebrew]: http://brew.sh/
-[fix_oralib]: https://github.com/kubo/fix_oralib_osx
-[Oracle Technology Network]: http://www.oracle.com/technetwork/topics/intel-macsoft-096467.html
+[OTN]: https://www.oracle.com/database/technologies/instant-client/macos-intel-x86-downloads.html#ic_osx_inst
+[Xcode]: https://apps.apple.com/us/app/xcode/id497799835
+[`rbenv`]: https://github.com/rbenv/rbenv