Improve backends handling and make DECOMPRESSION_BACKEND and PDF_BACKEND settings easier to discover

cmake/BackendHelpers.cmake

@@ -0,0 +1,44 @@
+include_guard(GLOBAL)
+
+function(yacreader_get_windows_arch_subdir out_var)
+    if(CMAKE_SYSTEM_PROCESSOR STREQUAL "ARM64" OR CMAKE_CXX_COMPILER_ARCHITECTURE_ID STREQUAL "ARM64")
+        set(_arch "arm64")
+    elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
+        set(_arch "x86")
+    else()
+        set(_arch "x64")
+    endif()
+
+    set(${out_var} "${_arch}" PARENT_SCOPE)
+endfunction()
+
+function(yacreader_add_imported_library target_name)
+    set(options)
+    set(oneValueArgs TYPE LOCATION IMPORTED_IMPLIB INCLUDE_DIR)
+    set(multiValueArgs LINK_LIBRARIES)
+    cmake_parse_arguments(YR "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+
+    if(NOT YR_TYPE)
+        set(YR_TYPE UNKNOWN)
+    endif()
+
+    if(NOT TARGET "${target_name}")
+        add_library("${target_name}" ${YR_TYPE} IMPORTED GLOBAL)
+    endif()
+
+    if(YR_LOCATION)
+        set_property(TARGET "${target_name}" PROPERTY IMPORTED_LOCATION "${YR_LOCATION}")
+    endif()
+
+    if(YR_IMPORTED_IMPLIB)
+        set_property(TARGET "${target_name}" PROPERTY IMPORTED_IMPLIB "${YR_IMPORTED_IMPLIB}")
+    endif()
+
+    if(YR_INCLUDE_DIR)
+        set_property(TARGET "${target_name}" PROPERTY INTERFACE_INCLUDE_DIRECTORIES "${YR_INCLUDE_DIR}")
+    endif()
+
+    if(YR_LINK_LIBRARIES)
+        set_property(TARGET "${target_name}" PROPERTY INTERFACE_LINK_LIBRARIES "${YR_LINK_LIBRARIES}")
+    endif()
+endfunction()