Modernize examples

Signed-off-by: Jeremie Dimino <jeremie@dimino.org>

example/sample-projects/hello_world/README.org

@@ -5,18 +5,18 @@ The library is defined in =lib= and the executable in =bin=. It also
 defines a test in =test=.
 
 At the toplevel of the project, there is a =hello_world.opam=
-file. This file is required so that =jbuilder= knows that this is the
+file. This file is required so that =dune= knows that this is the
 =hello_world= project.
 
 To build everything that is meant to be installed in this project,
 type:
 
 #+begin_src
-$ jbuilder build @install
+$ dune build @install
 #+end_src
 
 To run the tests, type:
 
 #+begin_src
-$ jbuilder runtest
+$ dune runtest
 #+end_src

example/sample-projects/hello_world/hello_world.opam

@@ -1,11 +1,11 @@
-opam-version: "1.2"
+opam-version: "2.0"
 version: "1.0"
 maintainer: "bob@sponge.com"
 authors: ["SpongeBob"]
 homepage: "https://github.com/SpongeBob/hello_world"
 bug-reports: "https://github.com/SpongeCob/hello_world/issues"
-dev-repo: "https://github.com/SpongeBob/hello_world.git"
+dev-repo: "git+https://github.com/SpongeBob/hello_world.git"
 license: "Apache-2.0"
 build: [
-  ["jbuilder" "build" "--only" "hello_world" "--root" "." "-j" jobs "@install"]
+  ["dune" "build" "-p" name "-j" jobs]
 ]

example/sample-projects/with-configure-step/README.org

@@ -1,5 +1,5 @@
 This project shows how to add a configure step to a project using
-jbuilder.
+dune.
 
 In order to keep things composable, it offers several way to configure
 the project:
@@ -27,10 +27,10 @@ Technically this is how it works:
 =config.full= is what is used by the rest of the build.
 
 Now in order to support (2) and (3), we setup the following rules in
-the toplevel =jbuild=:
+the toplevel =dune= file:
 - a rule to produce =config= by copying =config.default=
 - a rule to produce =config.full= by running =real_configure.ml=
 
-The reason it all work as described is because if Jbuilder knows how
+The reason it all work as described is because if Dune knows how
 to build a file and this file is already present in the source tree,
 it will always prefer the file that's already there

example/sample-projects/with-configure-step/myproject.opam

@@ -1,11 +1,11 @@
-opam-version: "1.2"
+opam-version: "2.0"
 version: "1.0"
 maintainer: "bob@sponge.com"
 authors: ["SpongeBob"]
 homepage: "https://github.com/SpongeBob/myproject"
 bug-reports: "https://github.com/SpongeCob/myproject/issues"
-dev-repo: "https://github.com/SpongeBob/myproject.git"
+dev-repo: "git+https://github.com/SpongeBob/myproject.git"
 license: "Apache-2.0"
 build: [
-  ["jbuilder" "build" "--only" "myproject" "--root" "." "-j" jobs "@install"]
+  ["dune" "build" "-p" name "-j" jobs]
 ]