Use pkg-config to find libarchive so static linking works

Author: Martchus

CMakeLists.txt

@@ -215,7 +215,14 @@ if (USE_LIBARCHIVE)
     if (NOT USE_STANDARD_FILESYSTEM)
         message(FATAL_ERROR "Unable to use USE_LIBARCHIVE without USE_STANDARD_FILESYSTEM.")
     endif ()
-    use_package(TARGET_NAME LibArchive::LibArchive PACKAGE_NAME LibArchive)
+    # use either the CMake find module or the pkg-config file to find libarchive; the latter is preferred as the CMake find
+    # module does not take transitive dependencies into account and thus breaks static linking
+    option(USE_LIBARCHIVE_VIA_FIND_MODULE "uses the CMake find module to find libarchive" OFF)
+    if (USE_LIBARCHIVE_VIA_FIND_MODULE)
+        use_package(TARGET_NAME LibArchive::LibArchive PACKAGE_NAME LibArchive)
+    else ()
+        use_pkg_config_module(PKG_CONFIG_MODULES "libarchive" TARGET_NAME LibArchive::LibArchive VISIBILITY PRIVATE)
+    endif ()
     list(APPEND HEADER_FILES io/archive.h)
     list(APPEND SRC_FILES io/archive.cpp)
     list(APPEND META_PUBLIC_COMPILE_DEFINITIONS ${META_PROJECT_VARNAME}_USE_LIBARCHIVE)