gnu: mrustc: Fix deserialization bug in communication with the procedural

macro compiler plugin.

* gnu/packages/patches/mrustc-0.8.0-fix-variable-length-integer-receiving.patch:
New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/rust.scm (mrustc)[source]: Use it.

Co-authored-by: Chris Marusich <cmmarusich@gmail.com>

gnu/local.mk

@@ -1046,6 +1046,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/mozjs38-tracelogger.patch		\
   %D%/packages/patches/mozjs38-version-detection.patch		\
   %D%/packages/patches/mrrescue-support-love-11.patch		\
+  %D%/packages/patches/mrustc-0.8.0-fix-variable-length-integer-receiving.patch \
   %D%/packages/patches/mumble-1.2.19-abs.patch			\
   %D%/packages/patches/mumps-build-parallelism.patch		\
   %D%/packages/patches/mupen64plus-ui-console-notice.patch	\

gnu/packages/patches/mrustc-0.8.0-fix-variable-length-integer-receiving.patch

@@ -0,0 +1,15 @@
+https://github.com/thepowersgang/mrustc/issues/109
+From: Danny Milosavljevic <dannym@scratchpost.org>
+Date: Fri, 3 Jan 2019 13:00:00 +0100
+
+--- mrustc/src/expand/proc_macro.cpp.orig	2019-02-01 14:16:54.208486062 +0100
++++ mrustc/src/expand/proc_macro.cpp	2019-02-01 14:17:14.350925705 +0100
+@@ -977,7 +977,7 @@
+     for(;;)
+     {
+         auto b = recv_u8();
+-        v |= static_cast<uint64_t>(b) << ofs;
++        v |= static_cast<uint64_t>(b & 0x7F) << ofs;
+         if( (b & 0x80) == 0 )
+             break;
+         ofs += 7;

gnu/packages/rust.scm

@@ -105,7 +105,9 @@
                 (file-name (git-file-name name version))
                 (sha256
                  (base32
-                  "0a7v8ccyzp1sdkwni8h1698hxpfz2sxhcpx42n6l2pbm0rbjp08i"))))
+                  "0a7v8ccyzp1sdkwni8h1698hxpfz2sxhcpx42n6l2pbm0rbjp08i"))
+                (patches
+                 (search-patches "mrustc-0.8.0-fix-variable-length-integer-receiving.patch"))))
       (outputs '("out" "cargo"))
       (build-system gnu-build-system)
       (inputs