guix: patch LIEF to fix PPC64 NX default

This patches our LIEF build using the change merged upstream:
lief-project/LIEF#718.

This can be dropped the next time we update LIEF.

Author: fanquake

contrib/guix/manifest.scm

@@ -200,6 +200,10 @@ chain for " target " development."))
   (package-with-extra-patches base-nsis
     (search-our-patches "nsis-gcc-10-memmove.patch")))
 
+(define (fix-ppc64-nx-default lief)
+  (package-with-extra-patches lief
+    (search-our-patches "lief-fix-ppc64-nx-default.patch")))
+
 (define-public lief
   (package
    (name "python-lief")
@@ -602,7 +606,7 @@ inspecting signatures in Mach-O binaries.")
         ;; Git
         git
         ;; Tests
-        lief)
+        (fix-ppc64-nx-default lief))
   (let ((target (getenv "HOST")))
     (cond ((string-suffix? "-mingw32" target)
            ;; Windows

contrib/guix/patches/lief-fix-ppc64-nx-default.patch

@@ -0,0 +1,29 @@
+Correct default for Binary::has_nx on ppc64
+
+From the Linux kernel source:
+
+    * This is the default if a program doesn't have a PT_GNU_STACK
+    * program header entry. The PPC64 ELF ABI has a non executable stack
+    * stack by default, so in the absence of a PT_GNU_STACK program header
+    * we turn execute permission off.
+
+This patch can be dropped the next time we update LIEF.
+
+diff --git a/src/ELF/Binary.cpp b/src/ELF/Binary.cpp
+index a90be1ab..fd2d9764 100644
+--- a/src/ELF/Binary.cpp
++++ b/src/ELF/Binary.cpp
+@@ -1084,7 +1084,12 @@ bool Binary::has_nx() const {
+                                        return segment->type() == SEGMENT_TYPES::PT_GNU_STACK;
+                                      });
+   if (it_stack == std::end(segments_)) {
+-    return false;
++    if (header().machine_type() == ARCH::EM_PPC64) {
++      // The PPC64 ELF ABI has a non-executable stack by default.
++      return true;
++    } else {
++      return false;
++    }
+   }
+ 
+   return !(*it_stack)->has(ELF_SEGMENT_FLAGS::PF_X);