gnu: mrustc: Update to 0.11.0-1.5e01a76.

* gnu/packages/rust.scm (%mrustc-commit): Update to newest commit.
(%mrustc-source): Update to 0.11.0-1.5e01a76.  Add a patch.  Adjust the
snippet to not use vendored openssl.
(rust-bootstrap)[source]: Remove patch, remove patch-flags.  Add to the
snippet a substitution for compatibility with llvm-13.
[inputs]: Remove input labels.  Remove conditional use of clang.
[arguments]: Allow parallel building on all architectures.  Update the
make-flags.  Replace the 'unpack phase to unpack the mrustc sources.
Delete the custom 'set-mrustc-sources and 'patch-cargo-checksum phases.
Adjust the custom 'patch-makefiles phase.  Adjust the 'configure and
'build phases to no longer use clang on some architectures.
* gnu/packages/patches/mrustc-patches.patch: New file.
* gnu/packages/patches/rustc-1.54.0-src.patch: Remove file.
* gnu/local.mk (dist_patch_DATA): Update it.

Change-Id: I7e444abe4b386b1bb77f05a278ddef45152ddb3c

gnu/packages/patches/mrustc-patches.patch

@@ -0,0 +1,19 @@
+diff --git a/rustc-1.54.0-src.patch b/rustc-1.54.0-src.patch
+index 088c723a..d322fd0d 100644
+--- a/rustc-1.54.0-src.patch
++++ b/rustc-1.54.0-src.patch
+@@ -302,14 +302,3 @@
+  use self::generic as arch;
+  
+  pub use self::arch::{vec128_storage, vec256_storage, vec512_storage};
+-
+---- src/llvm-project/llvm/include/llvm/Support/Signals.h
+-+++ src/llvm-project/llvm/include/llvm/Support/Signals.h
+-@@ -14,6 +14,7 @@
+- #ifndef LLVM_SUPPORT_SIGNALS_H
+- #define LLVM_SUPPORT_SIGNALS_H
+- 
+-+#include <cstdint>
+- #include <string>
+- 
+- namespace llvm {