Make CMake install arch independent (nonstd-lite issue 32)

- martinmoene/nonstd-lite-project#32

CMakeLists.txt

@@ -88,10 +88,9 @@ configure_package_config_file(
     INSTALL_DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${package_folder}"
 )
 
-write_basic_package_version_file(
-    "${CMAKE_CURRENT_BINARY_DIR}/${package_config_version}"
-    VERSION       ${package_version}
-    COMPATIBILITY SameMajorVersion
+configure_file(
+   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/${package_name}-config-version.cmake.in"
+   "${CMAKE_CURRENT_BINARY_DIR}/${package_config_version}" @ONLY
 )
 
 # Installation:

cmake/value_ptr-lite-config-version.cmake.in

@@ -0,0 +1,24 @@
+# Adapted from write_basic_package_version_file(... COMPATIBILITY SameMajorVersion) output
+# ARCH_INDEPENDENT is only present in cmake 3.14 and onwards
+
+set( PACKAGE_VERSION "@package_version@" )
+
+if( PACKAGE_VERSION VERSION_LESS PACKAGE_FIND_VERSION )
+    set( PACKAGE_VERSION_COMPATIBLE FALSE )
+else()
+    if( "@package_version@" MATCHES "^([0-9]+)\\." )
+        set( CVF_VERSION_MAJOR "${CMAKE_MATCH_1}" )
+    else()
+        set( CVF_VERSION_MAJOR "@package_version@" )
+    endif()
+
+    if( PACKAGE_FIND_VERSION_MAJOR STREQUAL CVF_VERSION_MAJOR )
+        set( PACKAGE_VERSION_COMPATIBLE TRUE )
+    else()
+        set( PACKAGE_VERSION_COMPATIBLE FALSE )
+    endif()
+
+    if( PACKAGE_FIND_VERSION STREQUAL PACKAGE_VERSION )
+        set( PACKAGE_VERSION_EXACT TRUE )
+    endif()
+endif()