gnu: libwebp: Update to 1.0.0.

* gnu/packages/image.scm (libwebp): Update to 1.0.0.
[source]: Change to GIT-FETCH.
[arguments]: Add 'bootstrap' phase.

gnu/packages/image.scm

@@ -846,16 +846,18 @@ multi-dimensional image processing.")
 (define-public libwebp
   (package
     (name "libwebp")
-    (version "0.6.1")
+    (version "1.0.0")
     (source
      (origin
-       (method url-fetch)
-       (uri (string-append
-             "http://downloads.webmproject.org/releases/webp/libwebp-" version
-             ".tar.gz"))
+       ;; No tarballs are provided for >0.6.1.
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://chromium.googlesource.com/webm/libwebp")
+             (commit (string-append "v" version))))
+       (file-name (git-file-name name version))
        (sha256
         (base32
-         "1ayq2zq0zbgf5yizbm32zh7p1vb8kibw74am6am1n5cz5mw3ql06"))))
+         "1w8jzdbr1s4238ygyrlxryycss3f2z6d9amxdq8m82nl3l6skar4"))))
     (build-system gnu-build-system)
     (inputs
      `(("freeglut" ,freeglut)
@@ -863,10 +865,18 @@ multi-dimensional image processing.")
        ("libjpeg" ,libjpeg)
        ("libpng" ,libpng)
        ("libtiff" ,libtiff)))
+    (native-inputs
+     `(("autoconf" ,autoconf)
+       ("automake" ,automake)
+       ("libtool" ,libtool)))
     (arguments
      '(#:configure-flags '("--enable-libwebpmux"
                            "--enable-libwebpdemux"
-                           "--enable-libwebpdecoder")))
+                           "--enable-libwebpdecoder")
+       #:phases (modify-phases %standard-phases
+                  (add-after 'unpack 'bootstrap
+                    (lambda _
+                      (invoke "autoreconf" "-vif"))))))
     (home-page "https://developers.google.com/speed/webp/")
     (synopsis "Lossless and lossy image compression")
     (description