gnu: Add meson-for-build.

* gnu/packages/build-tools.scm (meson-for-build): New variable.
* gnu/packages/patches/meson-for-build-rpath.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

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

gnu/local.mk

@@ -856,6 +856,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/mcrypt-CVE-2012-4527.patch			\
   %D%/packages/patches/mesa-skip-disk-cache-test.patch		\
   %D%/packages/patches/mesa-wayland-egl-symbols-check-mips.patch	\
+  %D%/packages/patches/meson-for-build-rpath.patch		\
   %D%/packages/patches/metabat-fix-compilation.patch		\
   %D%/packages/patches/mhash-keygen-test-segfault.patch		\
   %D%/packages/patches/mingw-w64-5.0rc2-gcc-4.9.3.patch		\

gnu/packages/build-tools.scm

@@ -93,6 +93,24 @@ files}, are written in a custom domain-specific language (DSL) that resembles
 Python.")
     (license license:asl2.0)))
 
+(define-public meson-for-build
+  (package
+    (inherit meson)
+    (name "meson-for-build")
+    (version "0.42.0")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "https://github.com/mesonbuild/meson/"
+                                  "archive/" version ".tar.gz"))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32
+                "0vyp9rkymzzzilhnf04ryszslyp9a0y0wf4agyijd4w5lcnqlcbc"))
+              (patches (search-patches "meson-for-build-rpath.patch"))))
+
+    ;; People should probably install "meson", not "meson-for-build".
+    (properties `((hidden? . #t)))))
+
 (define-public premake4
   (package
     (name "premake")

gnu/packages/patches/meson-for-build-rpath.patch

@@ -0,0 +1,24 @@
+This patch removes a part of meson that clears the rpath upon installation.
+This will only be applied to a special version of meson, used for the
+meson-build-system.
+
+Patch by Peter Mikkelsen <petermikkelsen10@gmail.com>
+
+--- meson-0.42.0/mesonbuild/scripts/meson_install.py.orig	2017-09-09 01:49:39.147374148 +0200
++++ meson-0.42.0/mesonbuild/scripts/meson_install.py	2017-09-09 01:51:01.209134717 +0200
+@@ -345,15 +345,6 @@
+                     print("Symlink creation does not work on this platform. "
+                           "Skipping all symlinking.")
+                     printed_symlink_error = True
+-        if is_elf_platform() and os.path.isfile(outname):
+-            try:
+-                e = depfixer.Elf(outname, False)
+-                e.fix_rpath(install_rpath)
+-            except SystemExit as e:
+-                if isinstance(e.code, int) and e.code == 0:
+-                    pass
+-                else:
+-                    raise
+
+ def run(args):
+     global install_log_file