gnu: faust-2: Update to 2.41.1.

* gnu/packages/audio.scm (faust-2): Update to 2.41.1.
[build-system]: Replace gnu-build-system with cmake-build-system.
[arguments]<#:phases>: Invoke cmake directly to build the main package
and invoke make directly to build ancillary tools.
[native-inputs]: Replace llvm-3.8 with llvm.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/audio.scm

@@ -1952,7 +1952,7 @@ also play midifiles using a Soundfont.")
 (define-public faust-2
   (package
     (inherit faust)
-    (version "2.5.23")
+    (version "2.41.1")
     (source (origin
               (method url-fetch)
               (uri (string-append "https://github.com/grame-cncm/faust/"
@@ -1960,15 +1960,29 @@ also play midifiles using a Soundfont.")
                                   "/faust-" version ".tar.gz"))
               (sha256
                (base32
-                "1yz5jnr76hh7rmxkpdi7gyrw1wp4gyqfpq8zyl97qdi5ga5gjznq"))))
-    (build-system gnu-build-system)
+                "0gk8ifxrbykq7ay0nvjns8fjryhp0wfhv5npgrl8xpgw9wfmw53j"))))
+    (build-system cmake-build-system)
     (arguments
-     (substitute-keyword-arguments (package-arguments faust)
-       ((#:make-flags flags)
-        `(list (string-append "prefix=" (assoc-ref %outputs "out"))
-               "world"))))
+     `(#:tests? #f ; no tests
+       #:phases
+       (modify-phases %standard-phases
+         ;; The upstream package uses make to run cmake during the build stage.
+         ;; Here we ignore the Makefile and call cmake directly.
+         (replace 'configure
+           (lambda _
+             (chdir "build")
+             (invoke "cmake" "-C" "backends/all.cmake"
+                     (string-append "-DCMAKE_INSTALL_PREFIX="
+                      (assoc-ref %outputs "out")))))
+         ;; The sound2faust tool would be built in the Makefile's "world" target
+         (add-after 'install 'sound2faust
+           (lambda _
+             (chdir "../tools/sound2faust")
+             (setenv "PREFIX" (assoc-ref %outputs "out"))
+             (invoke "make")
+             (invoke "make" "install"))))))
     (native-inputs
-     `(("llvm" ,llvm-3.8)
+     `(("llvm" ,llvm)
        ("which" ,which)
        ("xxd" ,xxd)
        ("ctags" ,emacs-minimal)  ; for ctags