gnu: bzip2: Fix script interpreters when cross-compiling.

Add bash-minimal as an input fixes the interpreters for various scripts (like
bzdiff and bzgrep) when cross-compiling.

* gnu/packages/compression.scm (bzip2)[inputs]: Add bash-minimal when cross
compiling.

gnu/packages/compression.scm

@@ -394,6 +394,10 @@ file; as a result, it is often used in conjunction with \"tar\", resulting in
        ,@(if (%current-target-system)
              '(#:tests? #f)
              '())))
+    (inputs
+     `(,@(if (%current-target-system)
+             `(("bash" ,bash-minimal))
+             '())))
     (outputs '("out" "static"))
     (synopsis "High-quality data compression program")
     (description