gnu: american-fuzzy-lop: Change custom qemu input.

* gnu/packages/debug.scm (american-fuzzy-lop)[inputs]: Custom-qemu now
inherits from private qemu-minimal-2.10.
* gnu/packages/bootloaders.scm (qemu-minimal-2.10): Add note to move
variable to gnu/packages/debug.scm when no longer needed in
bootloaders.scm.

gnu/packages/bootloaders.scm

@@ -74,6 +74,7 @@
 ;; The GRUB test suite fails with later versions of Qemu, so we
 ;; keep it at 2.10 for now.  See
 ;; <https://lists.gnu.org/archive/html/bug-grub/2018-02/msg00004.html>.
+;; TODO: When grub no longer needs this version, move to gnu/packages/debug.scm.
 (define qemu-minimal-2.10
   (package
     (inherit qemu-minimal)

gnu/packages/debug.scm

@@ -169,7 +169,7 @@ tools that process C/C++ code.")
       (inputs
        `(("custom-qemu"
           ;; The afl-qemu tool builds qemu 2.10.0 with a few patches applied.
-          ,(package (inherit qemu-minimal)
+          ,(package (inherit (@@ (gnu packages bootloaders) qemu-minimal-2.10))
              (name "afl-qemu")
              (inputs
               `(("afl-src" ,source)