Ports/backward-cpp: Link against zstd if present

Previously, the build would fail when the `zstd` port was already
installed.

Ports/backward-cpp/patches/0002-backward-Pretend-to-be-Linux-with-some-modifications.patch

@@ -8,7 +8,7 @@ Subject: [PATCH] backward: Pretend to be Linux, with some modifications
  1 file changed, 10 insertions(+), 3 deletions(-)
 
 diff --git a/backward.hpp b/backward.hpp
-index 670aa45853997c515974bb9411d7a9e72aeeee78..25e70cc6d0d1e508ac42e63ea3fa8b56992cfb27 100644
+index 670aa45853997c515974bb9411d7a9e72aeeee78..ff51271a9490d3f16520ca459849d384b3f2061a 100644
 --- a/backward.hpp
 +++ b/backward.hpp
 @@ -63,7 +63,7 @@

Ports/backward-cpp/patches/0003-Link-to-zstd-library.patch

@@ -0,0 +1,23 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Tim Ledbetter <timledbetter@gmail.com>
+Date: Fri, 18 Aug 2023 06:36:54 +0100
+Subject: [PATCH] Link to zstd library
+
+---
+ BackwardConfig.cmake | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/BackwardConfig.cmake b/BackwardConfig.cmake
+index cda0568bf9eaf76e7a3e263c1bd1aa950d1308a3..cd93ee07af2daf32fa2f1b6f550fcc8844c7215e 100644
+--- a/BackwardConfig.cmake
++++ b/BackwardConfig.cmake
+@@ -156,6 +156,9 @@ if (${STACK_DETAILS_AUTO_DETECT})
+ 			if (LIBSFRAME_LIBRARY)
+ 				list(APPEND _BACKWARD_LIBRARIES ${LIBSFRAME_LIBRARY})
+ 			endif()
++			if (LIBZSTD_LIBRARY)
++				list(APPEND _BACKWARD_LIBRARIES ${LIBZSTD_LIBRARY})
++			endif()
+ 
+ 			list(APPEND _BACKWARD_LIBRARIES iberty z)
+ 		endif()

Ports/backward-cpp/patches/ReadMe.md

@@ -10,3 +10,8 @@ test: Don't use program_invocation_name on Serenity
 backward: Pretend to be Linux, with some modifications
 
 
+## `0003-Link-to-zstd-library.patch`
+
+Link to zstd library
+
+