[Cpp] CMake: use variables for specifying install paths consistently

This allows overriding them if needed when the system uses different paths than
usual (e.g. Haiku, which uses "develop/headers" for includes instead of
"include").

Signed-off-by: Joachim Mairböck <[email protected]>

Author: jmairboeck

runtime/Cpp/CMakeLists.txt

@@ -222,14 +222,14 @@ endif(ANTLR4_INSTALL)
 
 if(EXISTS LICENSE.txt)
 install(FILES LICENSE.txt
-        DESTINATION "share/doc/libantlr4")
+        DESTINATION ${CMAKE_INSTALL_DOCDIR})
 elseif(EXISTS ../../LICENSE.txt)
 install(FILES ../../LICENSE.txt
-    DESTINATION "share/doc/libantlr4")
+    DESTINATION ${CMAKE_INSTALL_DOCDIR})
 endif()
 
 install(FILES README.md VERSION
-    DESTINATION "share/doc/libantlr4")
+    DESTINATION ${CMAKE_INSTALL_DOCDIR})
 
 set(CPACK_PACKAGE_CONTACT "[email protected]")
 set(CPACK_PACKAGE_VERSION ${ANTLR_VERSION})

runtime/Cpp/runtime/CMakeLists.txt

@@ -148,7 +148,7 @@ install(TARGETS antlr4_static
         RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 
 install(DIRECTORY "${PROJECT_SOURCE_DIR}/runtime/src/"
-        DESTINATION "include/antlr4-runtime"
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/antlr4-runtime"
         COMPONENT dev
         FILES_MATCHING PATTERN "*.h"
         )