gnu: fifengine: Gexp arguments.

* gnu/packages/games.scm (fifengine)[arguments]: Rewrite as gexps.  Remove
input labels, top-level Python reference, and trailing #t's.

gnu/packages/games.scm

@@ -3733,19 +3733,18 @@ Widgets, and allows users to create more.")
                 "1y4grw25cq5iqlg05rnbyxw1njl11ypidnlsm3qy4sm3xxdvb0p8"))))
     (build-system cmake-build-system)
     (arguments
-     `(#:tests? #f            ; TODO The test running fails to run some tests.
+     (list #:tests? #f         ;TODO The test running fails to run some tests.
            #:configure-flags
-       (list
+           #~(list
               (string-append "-DOPENALSOFT_INCLUDE_DIR="
-                       (assoc-ref %build-inputs "openal")
-                       "/include/AL")
+                             (search-input-directory %build-inputs "include/AL"))
               (string-append "-DPYTHON_SITE_PACKAGES="
-                       (assoc-ref %outputs "out")
-                       "/lib/python"
-                       ,(version-major+minor (package-version python))
+                             #$output "/lib/python"
+                             #$(version-major+minor
+                                (package-version (this-package-input "python")))
                              "/site-packages"))
            #:phases
-       (modify-phases %standard-phases
+           #~(modify-phases %standard-phases
                (add-after 'unpack 'patch-run_tests.py
                  (lambda _
                    ;; Patch the test runner to exit with a status of 1 if any test
@@ -3753,8 +3752,7 @@ Widgets, and allows users to create more.")
                    (substitute* "run_tests.py"
                      (("ERROR\\. One or more tests failed!'\\)")
                       "ERROR. One or more tests failed!')
-\t\texit(1)"))
-             #t))
+\t\texit(1)"))))
                ;; Run tests after installation so that we can make use of the built
                ;; python modules.
                (delete 'check)
@@ -3766,7 +3764,8 @@ Widgets, and allows users to create more.")
                      (setenv "DISPLAY" ":1")
                      (setenv "XDG_RUNTIME_DIR" "/tmp")
                      ;; Run tests
-               (chdir ,(string-append "../" name "-" version))
+                     (chdir #$(string-append "../" (package-name this-package)
+                                             "-" (package-version this-package)))
                      (invoke "python3" "run_tests.py" "-a")))))))
     (inputs
      (list sdl2