Add build instructions

COMPILING.md

@@ -0,0 +1,89 @@
+## Build instructions
+
+#### Java compatibility note
+
+It is recommended to use JDK 1.8 for building Millfork.  
+If you have multiple Java versions installed, enter  
+`set JAVA_HOME=PATH_TO_JAVA\bin    ` (Windows)  
+`export JAVA_HOME=PATH_TO_JAVA/bin ` (Mac/Linux)  
+(where PATH_TO_JAVA is a path to one of your JDK installations)
+into the command line before running sbt to choose a JDK.
+
+### Building without tests
+
+Setting up the test suite for Millfork is tricky, so if you don't need the tests, you can remove them.
+
+#### Prerequisites
+
+* JDK 1.8
+
+* sbt
+
+#### Steps
+
+* delete the `src/test` directory
+
+* remove all test dependencies from `build.sbt`: 
+
+      "org.scalatest" %% "scalatest"
+      "com.codingrodent.microprocessor" % "Z80Processor"
+      "NeatMonster" % "Intel8086"
+      "com.loomcom.symon" % "symon"
+      "com.grapeshot" % "halfnes"
+      "eu.rekawek.coffeegb" % "coffee-gb"
+
+* navigate to the project directory 
+
+* run `sbt compile` to compile the project
+
+* run `sbt assembly` to build the executable jar file, it should appear in `target/scala-2.12`
+
+### Building with tests
+
+Test suite is useful if you plan on modifying the compiler. Some test dependencies need manual installation.
+
+#### Prerequisites
+
+* JDK 1.8 with Nashorn (tests don't work on newer versions)
+
+* sbt
+
+* Maven
+
+#### Steps
+
+* download the dependencies that are not available in a central repository:
+
+        https://github.com/sethm/symon/tree/71905fdb1998ee4f142260879504bc46cf27648f
+        https://github.com/andrew-hoffman/halfnes/tree/061
+        https://github.com/trekawek/coffee-gb/tree/coffee-gb-1.0.0
+        
+* for each of them, run `maven package` and `maven install`
+
+* navigate to the project directory 
+
+* run `sbt compile` to compile the project
+
+* run `sbt assemble` to build the executable jar file, it should appear in `target/scala-2.12`
+
+### Building a native executable
+
+This is experimental. 
+
+#### Prerequisites
+
+* an executable jar with Millfork (see above)
+
+* GraalVM 19 or later
+
+* native-image
+
+* other tools required by native-image, appropriate for your operating system and GraalVM version (for example, Windows SDK 7.1 on Windows) 
+
+* a lot of RAM
+
+#### Steps
+
+* navigate to the directory containing the jar, most likely `target/scala-2.12`
+
+* run `native-image -jar millfork.jar` to build a native executable for your operating system

README.md

@@ -5,7 +5,8 @@
 A middle-level programming language targeting 6502-based, 8080-based and Z80-based microcomputers. 
 
 For binary releases, see: https://github.com/KarolS/millfork/releases
-(latest: 0.3.2)
+(latest: 0.3.2).  
+For build instructions, see [Build instructions](./COMPILING.md).
 
 ## Features
 

build.sbt

@@ -62,6 +62,7 @@ releaseDist := {
   IO.copyFile(base / "src/3rd-party-licenses.txt", distDir / "3rd-party-licenses.txt")
   IO.copyFile(base / "CHANGELOG.md", distDir / "CHANGELOG.md")
   IO.copyFile(base / "README.md", distDir / "README.md")
+  IO.copyFile(base / "COMPILING.md", distDir / "COMPILING.md")
   def copyDir(name: String): Unit = {
     IO.createDirectory(distDir / name)
     IO.copyDirectory(base / name, distDir / name)