Generate and install exported targets configs

Once installed to a prefix, CMake's find_package(zsync2 ...) can be used to find libzsync2.

Author: TheAssassin

CMakeLists.txt

@@ -88,3 +88,6 @@ add_subdirectory(src)
 
 # add unit tests
 add_subdirectory(tests)
+
+# finally, generate export configs
+include(cmake/export.cmake)

cmake/export.cmake

@@ -0,0 +1,46 @@
+# make sure CMake won't export this package by default (valid from 3.15 onwards)
+cmake_minimum_required(VERSION 3.15)
+set(CMP0090 NEW)
+
+# set up installion of exported targets (consider libzsync2 a namespace for use in CMake)
+install(
+    TARGETS libzsync2
+    DESTINATION lib
+    EXPORT libzsync2
+)
+
+# allow import from current build tree
+export(
+    TARGETS libzsync2
+    NAMESPACE zsync2::
+    FILE libzsync2Targets.cmake
+)
+
+# allow import from install tree
+# note that the targets must be install(... EXPORT zsync) in order for this to work (consider libzsync2 a namespace)
+install(
+    EXPORT libzsync2
+    DESTINATION lib/cmake/zsync2
+)
+
+include(CMakePackageConfigHelpers)
+# generate the config file that is includes the exports
+configure_package_config_file(
+    "${CMAKE_CURRENT_LIST_DIR}/zsync2Config.cmake.in"
+    "${PROJECT_BINARY_DIR}/cmake/zsync2Config.cmake"
+    INSTALL_DESTINATION "lib/cmake/zsync2"
+    NO_SET_AND_CHECK_MACRO
+    NO_CHECK_REQUIRED_COMPONENTS_MACRO
+)
+
+write_basic_package_version_file(
+    "${PROJECT_BINARY_DIR}/cmake/zsync2ConfigVersion.cmake"
+    VERSION "${VERSION}"
+    COMPATIBILITY AnyNewerVersion
+)
+
+install(FILES
+    "${PROJECT_BINARY_DIR}/cmake/zsync2Config.cmake"
+    "${PROJECT_BINARY_DIR}/cmake/zsync2ConfigVersion.cmake"
+    DESTINATION lib/cmake/zsync2
+)

cmake/zsync2Config.cmake.in

@@ -0,0 +1,3 @@
+@PACKAGE_INIT@
+
+include ( "${CMAKE_CURRENT_LIST_DIR}/zsync2Targets.cmake" )