Add Makefile and build instructions

.gitignore

@@ -0,0 +1,3 @@
+/vars.mk
+/build/
+xcuserdata/

Makefile

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+PROJECT = ios-command-line-tool.xcodeproj
+
+include vars.mk
+
+.PHONY: all clean
+
+all:
+	xcodebuild \
+		-project "$(PROJECT)" \
+		ARCHS="arm64" \
+		DEVELOPMENT_TEAM="$(DEV_TEAM)" \
+		IPHONEOS_DEPLOYMENT_TARGET="$(IOS_TARGET)" \
+		build
+
+clean:
+	xcodebuild \
+		-project "$(PROJECT)" \
+		ARCHS="arm64" \
+		DEVELOPMENT_TEAM="$(DEV_TEAM)" \
+		IPHONEOS_DEPLOYMENT_TARGET="$(IOS_TARGET)" \
+		clean

README.md

@@ -8,6 +8,79 @@ Xcode can be persuaded to build standalone Mach-O executables for iOS as well.
 
 This technique has been tested with Xcode 9.3 and iOS 11.1.2.
 
+## Build on Your System
+
+Building the tool on your system requires updating signing information and deployment info. You
+can do that from Xcode or from the command line.
+
+In order to build on your system you need a developer account. You find out if you have one by
+running the `security find-identity` command below on macOS. If you get an output similar to the
+one below, you have a developer account:
+
+```
+XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX "iPhone Developer: AAAAAAA (BBBBBBBBBB)"
+```
+
+If you don't have a developer account you need to create one. See the instructions
+[here](https://stackoverflow.com/questions/39524148/requires-a-development-team-select-a-development-team-in-the-project-editor-cod).
+
+### Building on Xcode
+
+Open the `ios-command-line-tool.xcodeproj` folder in Xcode (by using `File -> Open` in Xcode),
+click on the `ios-command-line-tool` top icon in the project navigator (left side), then go to
+the `General` tab (in the middle view). In the `Signing` section choose your `Team`. Once you
+do that, other issues will disappear.
+
+You may need to enable the `Project Navigator` view in Xcode. You do that by using `View ->
+Navigators -> Show Project Navigator`.
+
+If you want to build for an earlier version of iOS, go to the `Deployment Info` section in the
+middle view and choose the `Deployment Target` of your choice.
+
+You can now build the executable in Xcode (`Product -> Build`). The executable file will by
+default be located in
+`~/Library/Developer/Xcode/DerivedData/ios-command-line-tool-XXXXXXXXXXXX/Build/Products/Debug-iphoneos/ios-command-line-tool`
+(see more on that [here](https://pewpewthespells.com/blog/xcode_build_locations.html)). For
+example:
+
+```
+$ file ~/Library/Developer/Xcode/DerivedData/ios-command-line-tool-ffawlhgezawmrmfewovgtsimimkd/Build/Products/Debug-iphoneos/ios-command-line-tool
+/Users/razvan/Library/Developer/Xcode/DerivedData/ios-command-line-tool-ffawlhgezawmrmfewovgtsimimkd/Build/Products/Debug-iphoneos/ios-command-line-tool: Mach-O 64-bit arm64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>
+```
+
+### Building on the Command Line
+
+You can bypass using Xcode IDE altogether and resort to using the command line. You use the
+`Makefile` and the `make` command.
+
+Similar to the Xcode configuration, you first need to choose your development team. Create a
+`vars.mk` file by copying `vars.mk.sample`:
+
+```
+cp vars.mk.sample vars.mk
+```
+
+Now update the `DEV_TEAM` and the `IOS_TARGET` variables to proper values. You can find out
+existing development teams by running the one liner below, as shown
+[here](https://answers.unity.com/questions/1248794/ios-build-error-devleopment-team.html).
+
+```
+security find-identity -v -p codesigning | awk -F \" '{if ($2) print $2}' | while read acct ; do security find-certificate -a -c "$acct" -p | openssl x509 -text | grep "^ *Subject:" | awk -v acct="$acct" -F , '{if ($3) {sub(/ *OU=/,"",$3);print $3","acct}}' ; done
+```
+
+In the `vars.mk` file update the `DEV_TEAM` with one of the team IDs from output lines above
+and the `IOS_TARGET` with the iOS version you want to use.
+
+Now use `make` build the executable. The executable will be located in
+`build/Release-iphoneos/ios-command-line-tool`:
+
+```
+$ file build/Release-iphoneos/ios-command-line-tool
+build/Release-iphoneos/ios-command-line-tool: Mach-O 64-bit arm64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>
+```
+
+You can use `make clean` to clean the project.
+
 ## License
 
 The ios-command-line-tool template is released into the public domain.

vars.mk.sample

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+DEV_TEAM = DEEG7TTSF2
+IOS_TARGET = 11.1