gnu: mesa-opencl, mesa-opencl-icd: Build all the LLVM targets again.

Reported by John Kehayias <john.kehayias@protonmail.com>
in <https://issues.guix.gnu.org/49794>.

* gnu/packages/patches/mesa-opencl-all-targets.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gl.scm (mesa-opencl)[source]: Use it.

gnu/local.mk

@@ -1414,6 +1414,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libmemcached-build-with-gcc7.patch	\
   %D%/packages/patches/libmhash-hmac-fix-uaf.patch		\
   %D%/packages/patches/mercurial-hg-extension-path.patch       \
+  %D%/packages/patches/mesa-opencl-all-targets.patch		\
   %D%/packages/patches/mesa-skip-tests.patch			\
   %D%/packages/patches/mescc-tools-boot.patch			\
   %D%/packages/patches/metabat-fix-compilation.patch		\

gnu/packages/gl.scm

@@ -471,6 +471,10 @@ from software emulation to complete hardware acceleration for modern GPUs.")
 (define-public mesa-opencl
   (package/inherit mesa
     (name "mesa-opencl")
+    (source (origin
+              (inherit (package-source mesa))
+              (patches (cons (search-patch "mesa-opencl-all-targets.patch")
+                             (origin-patches (package-source mesa))))))
     (arguments
      (substitute-keyword-arguments (package-arguments mesa)
        ((#:configure-flags flags)

gnu/packages/patches/mesa-opencl-all-targets.patch

@@ -0,0 +1,25 @@
+This patch restores LLVM targets needed for OpenCL, *reverting* this
+upstream commit:
+
+  From 80817b6e344258ac9b955f824ebf9019a0fc1610 Mon Sep 17 00:00:00 2001
+  From: Jesse Natalie <jenatali@microsoft.com>
+  Date: Wed, 18 Nov 2020 18:30:30 -0800
+  Subject: [PATCH] meson: Adjust Clover's required LLVM modules
+
+diff --git a/meson.build b/meson.build
+index 6d1607c35a3..f828eb80faa 100644
+--- b/meson.build
++++ a/meson.build
+@@ -1479,10 +1479,9 @@
+ endif
+ if with_gallium_opencl
+   llvm_modules += [
+-    'linker', 'coverage', 'instrumentation', 'ipo', 'irreader',
+-    'lto', 'option', 'objcarcopts', 'profiledata'
++    'all-targets', 'linker', 'coverage', 'instrumentation', 'ipo', 'irreader',
++    'lto', 'option', 'objcarcopts', 'profiledata',
+   ]
+-  llvm_optional_modules += ['frontendopenmp']
+ endif
+ if with_microsoft_clc
+   llvm_modules += ['target', 'linker', 'irreader', 'option', 'libdriver']