cmake: allow system zarchive library (#4786)

CMakeLists.txt

@@ -256,6 +256,7 @@ if (ENABLE_SYSTEM_LIBRARIES)
     find_package(VulkanMemoryAllocator 3.1.0 CONFIG)
     find_package(xbyak 7.07 CONFIG)
     find_package(xxHash 0.8.2 MODULE)
+    find_package(ZArchive 0.1.2 MODULE)
     find_package(ZLIB 1.3 MODULE)
     find_package(Zydis 5.0.0 MODULE)
     find_package(pugixml 1.14 CONFIG)

cmake/FindZArchive.cmake

@@ -0,0 +1,15 @@
+# SPDX-FileCopyrightText: Copyright 2026 shadPS4 Emulator Project
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+find_package(PkgConfig QUIET)
+pkg_search_module(ZARCHIVE QUIET IMPORTED_TARGET zarchive)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(ZArchive
+    REQUIRED_VARS ZARCHIVE_LINK_LIBRARIES
+    VERSION_VAR ZARCHIVE_VERSION
+)
+
+if (ZArchive_FOUND AND NOT TARGET ZArchive::zarchive)
+    add_library(ZArchive::zarchive ALIAS PkgConfig::ZARCHIVE)
+endif()

externals/CMakeLists.txt

@@ -395,8 +395,9 @@ set(protobuf_MSVC_STATIC_RUNTIME OFF CACHE BOOL "" FORCE)
 endif()
 add_subdirectory(protobuf EXCLUDE_FROM_ALL)
 
-# zstd (dependency of ZArchive)
-if (NOT TARGET libzstd_static)
+# ZArchive (.zar archive support)
+if (NOT TARGET ZArchive::zarchive)
+    # zstd (dependency of ZArchive)
     set(ZSTD_BUILD_PROGRAMS OFF CACHE BOOL "" FORCE)
     set(ZSTD_BUILD_SHARED OFF CACHE BOOL "" FORCE)
     set(ZSTD_BUILD_STATIC ON CACHE BOOL "" FORCE)
@@ -404,10 +405,7 @@ if (NOT TARGET libzstd_static)
     set(ZSTD_LEGACY_SUPPORT OFF CACHE BOOL "" FORCE)
     set(ZSTD_MULTITHREAD_SUPPORT OFF CACHE BOOL "" FORCE)
     add_subdirectory(zstd/build/cmake)
-endif()
 
-# ZArchive (.zar archive support)
-if (NOT TARGET zarchive)
     add_library(zarchive STATIC
         zarchive/src/zarchivereader.cpp
         zarchive/src/zarchivewriter.cpp