Avoid hard-coded '../lib' in ApplicationContextBase

Another hard-coded library directory lurking in ApplicationContextBase was
continuing to break relocatable builds on systems which default to 'lib64' as
their library directory name. Although the RPATH was fixed in bf5eaaa,
the relative path is also needed when we dynamically load the modules.

The CMake script now writes a RELATIVE_LIBDIR variable into config.h which
contains the relative part of the library directory (i.e. starting with ".."),
and this RELATIVE_LIBDIR is now used both to set the RPATH in CMakeLists.txt
and in ApplicationContextBase to load the modules.

CMakeLists.txt

@@ -20,14 +20,16 @@ include(GNUInstallDirs)
 set(CORE_MODULE_LIBRARY "libradiantcore")
 set(PKGDATADIR "${CMAKE_INSTALL_FULL_DATADIR}/darkradiant")
 set(PKGLIBDIR "${CMAKE_INSTALL_FULL_LIBDIR}/darkradiant")
-if (NOT ${ENABLE_RELOCATION})
+if (${ENABLE_RELOCATION})
+    set(RELATIVE_LIBDIR "../${CMAKE_INSTALL_LIBDIR}/darkradiant")
+else()
     set(HTMLDIR "${CMAKE_INSTALL_FULL_DATADIR}/doc/darkradiant")
 endif()
 
 # Build shared libraries by default
 option(BUILD_SHARED_LIBS "Build shared libraries" ON)
 if (${ENABLE_RELOCATION})
-    set(CMAKE_INSTALL_RPATH "$ORIGIN/../${CMAKE_INSTALL_LIBDIR}/darkradiant")
+    set(CMAKE_INSTALL_RPATH "$ORIGIN/${RELATIVE_LIBDIR}")
 else()
     set(CMAKE_INSTALL_RPATH "${PKGLIBDIR}")
 endif()

config.h.in

@@ -14,6 +14,10 @@
 /* Package library directory (e.g. /usr/lib/darkradiant) */
 #cmakedefine PKGLIBDIR "@PKGLIBDIR@"
 
+/* Relative library directory from binary (e.g. ../lib/darkradiant). Only
+ * defined if ENABLE_RELOCATION is defined. */
+#cmakedefine RELATIVE_LIBDIR "@RELATIVE_LIBDIR@"
+
 /* Package data directory (e.g. /usr/share/darkradiant) */
 #cmakedefine PKGDATADIR "@PKGDATADIR@"
 

libs/module/ApplicationContextBase.cpp

@@ -50,8 +50,8 @@ std::string ApplicationContextBase::getLibraryBasePath() const
 #if defined(__APPLE__)
 	return _appPath;
 #elif defined(POSIX)
-#   if defined(ENABLE_RELOCATION)
-	return _appPath + "../lib/darkradiant/";
+#   if defined(ENABLE_RELOCATION) && defined(RELATIVE_LIBDIR)
+	return _appPath + RELATIVE_LIBDIR;
 #   elif defined(PKGLIBDIR)
 	return PKGLIBDIR;
 #   else