Add commandline_hello examples

examples/commandline_hello.jl

@@ -0,0 +1,8 @@
+# A super-simple command line program that just prints hello.
+# Build this with the `commandline_app=true` flag in `BuildApp.build_app_bundle`.
+
+Base.@ccallable function julia_main(ARGS::Vector{String})::Cint
+    println("Oh hi, World!")
+    println("Current working directory: $(pwd())")
+    return 0
+end

test/build_examples/commandline_hello.jl

@@ -0,0 +1,7 @@
+using ApplicationBuilder; using BuildApp
+
+# Allow this file to be called either as a standalone file to build the above
+# example, or from runtests.jl using a provided builddir.
+isdefined(:builddir) || (builddir=nothing)  # nothing == default builddir.
+
+build_app_bundle(examples_hello, commandline_app=true, builddir=builddir)