Use GNUInstallDirs DOCDIR for installing the manual

diff --git a/build/cmake/contrib/gen_html/CMakeLists.txt b/build/cmake/contrib/gen_html/CMakeLists.txt
index 958e9d17333b0727af536499d7f3e8e7039063a2..c4062d475955f3a3836a85eca22092b28225e43d 100644 (file)
--- a/build/cmake/contrib/gen_html/CMakeLists.txt
+++ b/build/cmake/contrib/gen_html/CMakeLists.txt
@@ -27,4 +27,4 @@ ADD_CUSTOM_TARGET(zstd_manual.html ALL
                   ${GENHTML_BINARY} "${LIBVERSION}" "${LIBRARY_DIR}/zstd.h" "${PROJECT_BINARY_DIR}/zstd_manual.html"
                   DEPENDS gen_html COMMENT "Update zstd manual")
 
-INSTALL(FILES "${PROJECT_BINARY_DIR}/zstd_manual.html" DESTINATION "${CMAKE_INSTALL_PREFIX}/${DOC_INSTALL_DIR}")
+INSTALL(FILES "${PROJECT_BINARY_DIR}/zstd_manual.html" DESTINATION "${CMAKE_INSTALL_DOCDIR}")