Fix build instructions in hacking.md and justfile

The stdenv phases don’t actually do anything (at least not anymore),
and our justfile doesn’t behave the same as our docs.

This patch removes the stdenv phases from the docs, documents our
usage of just, and makes `just setup` heed `$mesonFlags`.

Fixes NixOS#413.
Fixes NixOS#414.

Change-Id: Ieb0b2a8ae420526238b5f9a73d7849ec6919995d

doc/manual/src/contributing/hacking.md

@@ -39,17 +39,19 @@ $ nix-shell -A native-clangStdenvPackages
 
 ### Building from the development shell
 
-As always you may run [stdenv's phases by name](https://nixos.org/manual/nixpkgs/unstable/#sec-building-stdenv-package-in-nix-shell), e.g.:
+You can build and test Lix with just:
 
 ```bash
-$ configurePhase
-$ buildPhase
-$ checkPhase
-$ installPhase
-$ installCheckPhase
+$ just setup
+$ just build
+$ just test --suite=check
+$ just install
+$ just test --suite=installcheck
 ```
 
-To build manually, however, use the following:
+(Check and installcheck may both be done after install, allowing you to omit the --suite argument entirely, but this is the order package.nix runs them in.)
+
+You can also build Lix manually:
 
 ```bash
 $ meson setup ./build "--prefix=$out" $mesonFlags
@@ -64,9 +66,7 @@ $ meson install -C build
 $ meson test -C build --suite=installcheck
 ```
 
-(Check and installcheck may both be done after install, allowing you to omit the --suite argument entirely, but this is the order package.nix runs them in.)
-
-This will install Lix to `$PWD/outputs`, the `/bin` of which is prepended to PATH in the development shells.
+In both cases, Lix will be installed to `$PWD/outputs`, the `/bin` of which is prepended to PATH in the development shells.
 
 If the tests fail and Meson helpfully has no output for why, use the `--print-error-logs` option to `meson test`.
 

justfile

@@ -10,7 +10,7 @@ clean:
 
 # Prepare meson for building
 setup:
-    meson setup build --prefix="$PWD/outputs/out"
+    meson setup build --prefix="$PWD/outputs/out" $mesonFlags
 
 # Build lix
 build *OPTIONS: