gnu: Add wabt.

* gnu/packages/web (wabt): New variable.
* gnu/packages/diffoscope (diffoscope)[native-inputs]: Add wabt for tests.
  [arguments]: Add phase patching wabt into known tools.

gnu/packages/diffoscope.scm

@@ -57,6 +57,7 @@
   #:use-module (gnu packages textutils)
   #:use-module (gnu packages video)
   #:use-module (gnu packages vim)
+  #:use-module (gnu packages web)
   #:use-module (guix build-system python)
   #:use-module (guix gexp)
   #:use-module (guix git-download)
@@ -88,6 +89,12 @@
                       (lambda _
                         (substitute* "setup.py"
                           (("'python-magic',") ""))))
+                    ;; Patch in support for known tools
+                    (add-after 'unpack 'add-known-tools
+                      (lambda _
+                        (substitute* "diffoscope/external_tools.py"
+                          (("'arch': 'wabt'},")
+                           "'arch': 'wabt', 'guix': 'wabt'},"))))
                     ;; This test is broken because our `file` package has a
                     ;; bug in berkeley-db file type detection.
                     (add-after 'unpack 'remove-berkeley-test
@@ -188,6 +195,7 @@
                        ("squashfs-tools" ,squashfs-tools)
                        ("tcpdump" ,tcpdump)
                        ("unzip" ,unzip)
+                       ("wabt" ,wabt)
                        ("xxd" ,xxd)
                        ("xz" ,xz)
                        ("zip" ,zip)))

gnu/packages/web.scm

@@ -123,6 +123,7 @@
   #:use-module (gnu packages pkg-config)
   #:use-module (gnu packages qt)
   #:use-module (gnu packages readline)
+  #:use-module (gnu packages re2c)
   #:use-module (gnu packages sphinx)
   #:use-module (gnu packages texinfo)
   #:use-module (gnu packages textutils)
@@ -859,6 +860,45 @@ for efficient socket-like bidirectional reliable communication channels.")
     ;; This is LGPLv2.1-only with extra exceptions specified in 'LICENSE'.
     (license license:lgpl2.1)))
 
+(define-public wabt
+  (package
+    (name "wabt")
+    (version "1.0.11")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/WebAssembly/wabt")
+             (commit version)))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32 "0hn88vlqyclpk79v3wg3lrssd9vwhjdgvb41g03jqakygxxgnmp5"))))
+    (build-system cmake-build-system)
+    (arguments
+     `(#:configure-flags '("-DBUILD_TESTS=OFF")
+       #:tests? #f))
+    (inputs `(("python" ,python-2)
+              ("re2c" ,re2c)))
+    (home-page "https://github.com/WebAssembly/wabt")
+    (synopsis "WebAssembly Binary Toolkit")
+    (description "WABT (pronounced: wabbit) is a suite of tools for
+WebAssembly, including:
+
+* wat2wasm: translate from WebAssembly text format to the WebAssembly binary
+  format
+* wasm2wat: the inverse of wat2wasm, translate from the binary format back
+  to the text format (also known as a .wat)
+* wasm-objdump: print information about a wasm binary.  Similar to objdump.
+* wasm-interp: decode and run a WebAssembly binary file using a stack-based
+  interpreter
+* wat-desugar: parse .wat text form as supported by the spec interpreter
+  (s-expressions, flat syntax, or mixed) and print canonical flat format
+* wasm2c: convert a WebAssembly binary file to a C source and header
+
+These tools are intended for use in (or for development of) toolchains or
+other systems that want to manipulate WebAssembly files.")
+    (license license:asl2.0)))
+
 (define-public websocketpp
   (package
     (name "websocketpp")