build, vm: Use "GuixSD" or "GUIXSD" as volume label.

* gnu/build/vm.scm (initialize-hard-disk): Use "GuixSD" as label.
* gnu/system/install.scm (installation-os): Use "GuixSD" as label.
* gnu/system/vm.scm (system-disk-image): Use "GuixSD" or "GUIXSD" as volume
label.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu/build/vm.scm

@@ -431,7 +431,7 @@ passing it a directory name where it is mounted."
           (lambda (port)
             (format port
                     "insmod part_msdos~@
-                    search --set=root --label gnu-disk-image~@
+                    search --set=root --label GuixSD~@
                     configfile /boot/grub/grub.cfg~%")))
 
         (display "creating EFI firmware image...")

gnu/system/install.scm

@@ -306,7 +306,7 @@ Use Alt-F2 for documentation.
      ;; the appropriate one.
      (cons* (file-system
               (mount-point "/")
-              (device "gnu-disk-image")
+              (device "GuixSD")
               (title 'label)
               (type "ext4"))
 

gnu/system/vm.scm

@@ -335,11 +335,17 @@ the image."
 system described by OS.  Said image can be copied on a USB stick as is.  When
 VOLATILE? is true, the root file system is made volatile; this is useful
 to USB sticks meant to be read-only."
+  (define normalize-label
+    ;; ISO labels are all-caps (case-insensitive), but since
+    ;; 'find-partition-by-label' is case-sensitive, make it all-caps here.
+    (if (string=? "iso9660" file-system-type)
+        string-upcase
+        identity))
   (define root-label
     ;; Volume name of the root file system.  Since we don't know which device
     ;; will hold it, we use the volume name to find it (using the UUID would
     ;; be even better, but somewhat less convenient.)
-    "gnu-disk-image")
+    (normalize-label "GuixSD"))
 
   (define file-systems-to-keep
     (remove (lambda (fs)