gnu: bcachefs-tools: Support FUSE.

* gnu/packages/file-systems.scm (bcachefs-tools)[arguments]:
Add a new 'enable-fuse phase.
[inputs]: Add fuse.

Change-Id: Ie82a361a4a6bfd0af7ce9c915bdc468f7aa06df2

gnu/packages/file-systems.scm

@@ -723,7 +723,8 @@ performance and other characteristics.")
     (license license:gpl2+)))
 
 (define-public bcachefs-tools
-  ;; The final public package with shell completion even when cross-compiling.
+  ;; The final public package with shell completion even when cross-compiling,
+  ;; as well as optional features such as FUSE (‘bcachefs fusemount’).
   (package
     (inherit bcachefs-tools-minimal)
     (name "bcachefs-tools")
@@ -737,6 +738,10 @@ performance and other characteristics.")
           (srfi srfi-26)))
        ((#:phases phases #~%standard-phases)
 	#~(modify-phases #$phases
+            (add-before 'build 'enable-fuse
+              (lambda _
+                ;; This must be an environment variable, not a make flag!
+                (setenv "BCACHEFS_FUSE" "1")))
 	    (add-after 'install 'install-completions
               (lambda* (#:key native-inputs #:allow-other-keys)
                 (define bcachefs
@@ -763,7 +768,10 @@ performance and other characteristics.")
      (append (package-native-inputs bcachefs-tools-minimal)
 	     (if (%current-target-system)
 		 (list bcachefs-tools-minimal)
-		 (list))))))
+		 (list))))
+    (inputs
+     (modify-inputs (package-inputs bcachefs-tools-minimal)
+       (append fuse)))))
 
 (define-public bcachefs-tools-minimal/static
   ;; The static variant is public for consistency with the other file system