Add Drone CI scripts (#8)

* Add Drone CI scripts

See https://discourse.julialang.org/t/testing-on-arm-with-drone-ci/25871

The jsonnet file is not strictly necessary, but it allows us to easily regenerate
the YAML in the future.  Tell if you don't want it.

* Enable ARM arch with Julia 1.0

Author: giordano

.drone.jsonnet

@@ -0,0 +1,24 @@
+local Pipeline(os, arch, version) = {
+    kind: "pipeline",
+    name: os+" - "+arch+" - Julia "+version,
+    platform: {
+	os: os,
+	arch: arch
+    },
+    steps: [
+	{
+	    name: "build",
+	    image: "julia:"+version,
+	    commands: [
+		"julia --project=. --check-bounds=yes --color=yes -e 'using InteractiveUtils; versioninfo(verbose=true); using Pkg; Pkg.build(); Pkg.test(coverage=true)'"
+	    ]
+	}
+    ]
+};
+
+[
+    Pipeline("linux", "arm",   "1.0"),
+    # Pipeline("linux", "arm",   "1.1"),
+    Pipeline("linux", "arm64", "1.0"),
+    Pipeline("linux", "arm64", "1.1")
+]

.drone.yml

@@ -0,0 +1,43 @@
+---
+kind: pipeline
+name: linux - arm - Julia 1.0
+
+platform:
+  os: linux
+  arch: arm
+
+steps:
+- name: build
+  image: julia:1.0
+  commands:
+  - "julia --project=. --check-bounds=yes --color=yes -e 'using InteractiveUtils; versioninfo(verbose=true); using Pkg; Pkg.build(); Pkg.test(coverage=true)'"
+
+---
+kind: pipeline
+name: linux - arm64 - Julia 1.0
+
+platform:
+  os: linux
+  arch: arm64
+
+steps:
+- name: build
+  image: julia:1.0
+  commands:
+  - "julia --project=. --check-bounds=yes --color=yes -e 'using InteractiveUtils; versioninfo(verbose=true); using Pkg; Pkg.build(); Pkg.test(coverage=true)'"
+
+---
+kind: pipeline
+name: linux - arm64 - Julia 1.1
+
+platform:
+  os: linux
+  arch: arm64
+
+steps:
+- name: build
+  image: julia:1.1
+  commands:
+  - "julia --project=. --check-bounds=yes --color=yes -e 'using InteractiveUtils; versioninfo(verbose=true); using Pkg; Pkg.build(); Pkg.test(coverage=true)'"
+
+...