doc: add macOS_Catalina.md document

PR-URL: #1940
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>

README.md

@@ -43,6 +43,7 @@ below) it will attempt to find a compatible Python executable.
    * Python v2.7, v3.5, v3.6, or v3.7
    * [Xcode](https://developer.apple.com/xcode/download/)
      * You also need to install the `XCode Command Line Tools` by running `xcode-select --install`. Alternatively, if you already have the full Xcode installed, you can find them under the menu `Xcode -> Open Developer Tool -> More Developer Tools...`. This step will install `clang`, `clang++`, and `make`.
+   * If your Mac has been _upgraded_ to macOS Catalina (10.15), please read [macOS_Catalina.md](macOS_Catalina.md).
 
 ### On Windows
 

macOS_Catalina.md

@@ -0,0 +1,69 @@
+# Installation notes for macOS Catalina (v10.15)
+
+_This document specifically refers to upgrades from previous versions of macOS to Catalina (10.15). It should be removed from the source repository when Catalina ceases to be the latest macOS version or updated to deal with challenges involved in upgrades to the next version of macOS._
+
+Lessons learned from:
+* https://github.com/nodejs/node-gyp/issues/1779
+* https://github.com/nodejs/node-gyp/issues/1861
+* https://github.com/nodejs/node-gyp/issues/1927 and elsewhere
+
+Installing `node-gyp` on macOS can be found at https://github.com/nodejs/node-gyp#on-macos
+
+However, upgrading to macOS Catalina changes some settings that may cause normal `node-gyp` installations to fail.
+
+### Is my Mac running macOS Catalina?
+Let's make first make sure that your Mac is currently running Catalina:
+% `sw_vers`
+    ProductName:	Mac OS X
+    ProductVersion:	10.15
+    BuildVersion:	19A602
+
+If `ProductVersion` is less then `10.15` then this document is not really for you.
+
+### The acid test
+Next, lets see if `Xcode Command Line Tools` are installed:
+1. `/usr/sbin/pkgutil --packages | grep CL`
+    * If nothing is listed, then [skip to the next section](#Two-roads).
+    * If `com.apple.pkg.CLTools_Executables` is listed then try:
+2. `/usr/sbin/pkgutil --pkg-info com.apple.pkg.CLTools_Executables`
+    * If `version: 11.0.0` or later is listed then _you are done_!  Your Mac should be ready to install `node-gyp`.  Doing `clang -v` should show `Apple clang version 11.0.0` or later.
+
+As you go through the remainder of this document, at anytime you can try these `acid test` commands. If they pass then your Mac should be ready to install `node-gyp`.
+
+### Two roads
+There are two main ways to install `node-gyp` on macOS:
+1. With the full Xcode (~7.6 GB download) from the `App Store` app.
+2. With the _much_ smaller Xcode Command Line Tools via `xcode-select --install`
+
+### Installing `node-gyp` using the full Xcode
+1. `xcodebuild -version` should show `Xcode 11.1` or later.
+    * If not, then install/upgrade Xcode from the App Store app.
+2. Open the Xcode app and allow it to do an essential install of the most recent compiler tools.
+3. Once all installations are _complete_, quit out of Xcode.
+4. `sudo xcodebuild -license accept`  # If you agree with the licensing terms.
+5. `softwareupdate -l`  # No listing is a good sign.
+    * If Xcode or Tools upgrades are listed, use "Software Upgrade" to install them.
+6. `xcode-select -version`  # Should return `xcode-select version 2370` or later.
+7. `xcode-select -print-path`  # Should return `/Applications/Xcode.app/Contents/Developer`
+8. Try the [_acid test_ steps above](#The-acid-test) to see if your Mac is ready.
+9. If the _acid test_ does _not_ pass then...
+10. `sudo xcode-select --reset`  # Enter root password.  No output is normal.
+11. Repeat step 7 above.  Is the path different this time?  Repeat the _acid test_.
+
+### Installing `node-gyp` using the Xcode Command Line Tools
+1. If the _acid test_ has not succeeded, then try `xcode-select --install`
+2. Wait until the install process is _complete_.
+3. `softwareupdate -l`  # No listing is a good sign.
+    * If Xcode or Tools upgrades are listed, use "Software Update" to install them.
+4. `xcode-select -version`  # Should return `xcode-select version 2370` or later.
+5. `xcode-select -print-path`  # Should return `/Library/Developer/CommandLineTools`
+6. Try the [_acid test_ steps above](#The-acid-test) to see if your Mac is ready.
+7. If the _acid test_ does _not_ pass then...
+8. `sudo xcode-select --reset`  # Enter root password.  No output is normal.
+9. Repeat step 5 above.  Is the path different this time?  Repeat the _acid test_.
+
+### I did all that and the acid test still does not pass :-(
+1. `sudo rm -rf $(xcode-select -print-path)`  # Enter root password.  No output is normal.
+2. `xcode-select --install`
+3. If the [_acid test_](#The-acid-test) still does _not_ pass then...
+4. Add a comment to https://github.com/nodejs/node-gyp/issues/1927 so we can improve.