build: Use 'option' instead of 'set' for build variables

CMakeLists.txt

@@ -24,16 +24,14 @@ endif()
 include(CMakePrintHelpers)
 
 
-# Configure which language(s) should be supported:
-set(BUILD_CXX_LANGUAGE_PACKAGE OFF CACHE BOOL "Add C/C++ support to the Sourcetrail indexer.")
-set(BUILD_JAVA_LANGUAGE_PACKAGE OFF CACHE BOOL "Add Java support to the Sourcetrail indexer.")
-set(BUILD_PYTHON_LANGUAGE_PACKAGE OFF CACHE BOOL "Add Python support to the Sourcetrail indexer.")
+# Configure which language(s)/package(s) should be supported:
+option(BUILD_CXX_LANGUAGE_PACKAGE    "Add C/C++ support to the Sourcetrail indexer." OFF)
+option(BUILD_JAVA_LANGUAGE_PACKAGE   "Add Java support to the Sourcetrail indexer." OFF)
+option(BUILD_PYTHON_LANGUAGE_PACKAGE "Add Python support to the Sourcetrail indexer." OFF)
+option(BUILD_UNIT_TESTS_PACKAGE      "Build the corresponding language unit tests." OFF)
 
 configure_file(cmake/language_packages.h.in src/lib/language_packages.h)
 
-# Configure whether unit tests should be supported:
-set(BUILD_UNIT_TESTS_PACKAGE OFF CACHE BOOL "Build the corresponding language unit tests.")
-
 # prohibit in-source-builds
 if (${CMAKE_BINARY_DIR} STREQUAL ${CMAKE_SOURCE_DIR})
 	message(FATAL_ERROR "In-source-builds are strongly discouraged and not supported!")