Add support for new build types.

* src/cuirass/specification.scm (%build-types): Add 'images, 'system-tests and
'tarball support.
* doc/cuirass.texi (Specifications): Adapt it.

doc/cuirass.texi

@@ -127,6 +127,15 @@ pull} command.
 @item @code{hello}
 Build only the hello package.
 
+@item @code{images}
+Build only the Guix System images.
+
+@item @code{system-tests}
+Build only the Guix System tests.
+
+@item @code{tarball}
+Build only the Guix binary tarball.
+
 @item @code{(channels . list)}
 Build only the packages that are part of the given channel
 @code{list}.  For instance, @code{(channels my-channel)} will only

src/cuirass/specification.scm

@@ -140,7 +140,16 @@
 
 ;; The list of possible build types.
 (define %build-types
-  '(all core guix hello channels packages manifests))
+  '(all
+    core
+    guix
+    hello
+    images
+    system-tests
+    tarball
+    channels
+    packages
+    manifests))
 
 (define-record-type* <specification>
   specification make-specification