Allow building only selected images

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

Jenkinsfile

@@ -112,6 +112,33 @@ def architectures = [
     ]
 ]
 
+properties([
+    parameters([
+        string(name: 'buildOnly', defaultValue: '', description: 'If set, only the selected images are built. Comma and slash separated, e.g. armhf/minimal, amd64/target', trim: true),
+    ])
+])
+
+def buildCandidates = [:]
+
+def buildOnlyList = params?.buildOnly.tokenize(/, ?/).collect { it.tokenize('/') }
+
+buildOnlyList = buildOnlyList
+  .groupBy{ it[0] }
+  .collectEntries{ arch, values -> [arch, values.findResults { it[1] } ] }
+
+buildCandidates = architectures
+  // filter out architectures which won't be built
+  .subMap(buildOnlyList.keySet())
+  .collectEntries{ arch, architecture ->
+    // filter out artifact types which won't be built
+    types = architecture.types
+    if (buildOnlyList[arch])
+        types = architecture.types.subMap(buildOnlyList[arch])
+    [arch, architecture + [
+      types: types
+    ]]
+  }
+
 // SSH complains loudly if the current user is not in the user database, so fake that
 def withSshAgent(credentials, command) {
   sshagent(credentials: [ credentials, ] ) {
@@ -478,7 +505,7 @@ def buildImages(architecture, type, boards, debosarguments = "", image = true, s
 def first_pass = [:]
 def second_pass = [:]
 
-architectures.each { name, arch ->
+buildCandidates.each { name, arch ->
     arch.types.each { type, params ->
         /* merge the per-arch default with per-type params */
         def merged = [:] << arch << params