FindEXPAT: backport from CMake, but with local changes

CMake/FindEXPAT.cmake

+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+# XXX: Copied from CMake, but includes vtkDetectLibraryType.
+# See https://gitlab.kitware.com/cmake/cmake/issues/18564
+
+#[=======================================================================[.rst:
+FindEXPAT
+---------
+
+Find the native Expat headers and library.
+
+Imported Targets
+^^^^^^^^^^^^^^^^
+
+This module defines the following :prop_tgt:`IMPORTED` targets:
+
+``EXPAT::EXPAT``
+  The Expat ``expat`` library, if found.
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+This module will set the following variables in your project:
+
+``EXPAT_INCLUDE_DIRS``
+  where to find expat.h, etc.
+``EXPAT_LIBRARIES``
+  the libraries to link against to use Expat.
+``EXPAT_FOUND``
+  true if the Expat headers and libraries were found.
+
+#]=======================================================================]
+
+find_package(PkgConfig QUIET)
+
+pkg_check_modules(PC_EXPAT QUIET expat)
+
+# Look for the header file.
+find_path(EXPAT_INCLUDE_DIR NAMES expat.h HINTS ${PC_EXPAT_INCLUDE_DIRS})
+
+# Look for the library.
+find_library(EXPAT_LIBRARY NAMES expat libexpat HINTS ${PC_EXPAT_LIBRARY_DIRS})
+
+if (EXPAT_INCLUDE_DIR AND EXISTS "${EXPAT_INCLUDE_DIR}/expat.h")
+    file(STRINGS "${EXPAT_INCLUDE_DIR}/expat.h" expat_version_str
+         REGEX "^#[\t ]*define[\t ]+XML_(MAJOR|MINOR|MICRO)_VERSION[\t ]+[0-9]+$")
+
+    unset(EXPAT_VERSION_STRING)
+    foreach(VPART MAJOR MINOR MICRO)
+        foreach(VLINE ${expat_version_str})
+            if(VLINE MATCHES "^#[\t ]*define[\t ]+XML_${VPART}_VERSION[\t ]+([0-9]+)$")
+                set(EXPAT_VERSION_PART "${CMAKE_MATCH_1}")
+                if(EXPAT_VERSION_STRING)
+                    string(APPEND EXPAT_VERSION_STRING ".${EXPAT_VERSION_PART}")
+                else()
+                    set(EXPAT_VERSION_STRING "${EXPAT_VERSION_PART}")
+                endif()
+            endif()
+        endforeach()
+    endforeach()
+endif ()
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(EXPAT
+                                  REQUIRED_VARS EXPAT_LIBRARY EXPAT_INCLUDE_DIR
+                                  VERSION_VAR EXPAT_VERSION_STRING)
+
+# Copy the results to the output variables and target.
+if(EXPAT_FOUND)
+  set(EXPAT_LIBRARIES ${EXPAT_LIBRARY})
+  set(EXPAT_INCLUDE_DIRS ${EXPAT_INCLUDE_DIR})
+
+  if(NOT TARGET EXPAT::EXPAT)
+    include(vtkDetectLibraryType)
+    vtk_detect_library_type(expat_library_type
+      PATH "${EXPAT_LIBRARY}")
+    add_library(EXPAT::EXPAT "${expat_library_type}" IMPORTED)
+    unset(expat_library_type)
+    set_target_properties(EXPAT::EXPAT PROPERTIES
+      IMPORTED_LINK_INTERFACE_LANGUAGES "C"
+      IMPORTED_LOCATION "${EXPAT_LIBRARY}"
+      INTERFACE_INCLUDE_DIRECTORIES "${EXPAT_INCLUDE_DIRS}")
+  endif()
+endif()
+
+mark_as_advanced(EXPAT_INCLUDE_DIR EXPAT_LIBRARY)