https://github.com/rtissera/libchdr/commit/25fcb10cde7b9af71dbbb76d68033a4975af0a08
https://github.com/rtissera/libchdr/pull/158

From 23d3ddda8332e3793e62e61ec57222b3d4c184e4 Mon Sep 17 00:00:00 2001
From: orbea <orbea@riseup.net>
Date: Sat, 2 May 2026 16:33:19 -0700
Subject: [PATCH] cmake: fallback to pkgconfig if the zstd cmake config is
 missing

Upstream zstd only installs the zstd cmake config file when its built
with cmake and several distros such as Gentoo use the official make
build system instead.

This makes depending on the cmake config file unreliable and for
downstream projects. Its better to fallback to using the pkgconfig file
when its not found.

This solution is copied from cemu.

Upstream-Issue: https://github.com/facebook/zstd/issues/3271
Source: https://github.com/cemu-project/Cemu/blob/9b76b0e2d33725d37dc8c6137d8ea2fa9b991542/cmake/Findzstd.cmake
---
 CMakeLists.txt       | 10 ++++------
 cmake/Findzstd.cmake | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 6 deletions(-)
 create mode 100644 cmake/Findzstd.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5cb20c9..5c52522 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,6 +29,8 @@ if(BUILD_FUZZER)
   set(BUILD_SHARED_LIBS OFF)
 endif()
 
+list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")
+
 include(GNUInstallDirs)
 
 #--------------------------------------------------
@@ -55,12 +57,8 @@ endif()
 
 # zstd
 if (WITH_SYSTEM_ZSTD)
-  find_package(zstd REQUIRED)
-  if(TARGET zstd::libzstd_shared)
-    list(APPEND PLATFORM_LIBS zstd::libzstd_shared)
-  else()
-    list(APPEND PLATFORM_LIBS zstd::libzstd_static)
-  endif()
+  find_package(zstd MODULE REQUIRED)
+  list(APPEND PLATFORM_LIBS zstd::zstd)
   list(APPEND CHDR_DEFINES CHDR_SYSTEM_ZSTD)
 else()
   if(NOT TARGET zstd)
diff --git a/cmake/Findzstd.cmake b/cmake/Findzstd.cmake
new file mode 100644
index 0000000..a8a45a6
--- /dev/null
+++ b/cmake/Findzstd.cmake
@@ -0,0 +1,33 @@
+# SPDX-FileCopyrightText: 2022 Andrea Pappacoda <andrea@pappacoda.it>
+# SPDX-License-Identifier: ISC
+
+include(FindPackageHandleStandardArgs)
+
+find_package(zstd CONFIG)
+if (zstd_FOUND)
+	# Use upstream zstdConfig.cmake if possible
+	if (NOT TARGET zstd::zstd)
+		if (TARGET zstd::libzstd_static)
+			add_library(zstd::zstd ALIAS zstd::libzstd_static)
+		elseif (TARGET zstd::libzstd_shared)
+			add_library(zstd::zstd ALIAS zstd::libzstd_shared)
+		endif()
+	endif()
+	find_package_handle_standard_args(zstd CONFIG_MODE)
+else()
+	# Fallback to pkg-config otherwise
+	find_package(PkgConfig)
+	if (PKG_CONFIG_FOUND)
+		pkg_search_module(libzstd IMPORTED_TARGET GLOBAL libzstd)
+		if (libzstd_FOUND)
+			add_library(zstd::zstd ALIAS PkgConfig::libzstd)
+		endif()
+	endif()
+
+	find_package_handle_standard_args(zstd
+		REQUIRED_VARS
+			libzstd_LINK_LIBRARIES
+			libzstd_FOUND
+		VERSION_VAR libzstd_VERSION
+	)
+endif()