Install binary and its shared library dependencies

Install the darkradiant binary and the shared libraries it links against
(wxutil, math etc), and set a relative -rpath so that the executable can find
its libraries. Unlike with Automake, the use of "$ORIGIN/.." just works without
needing to figure out how to escape the syntax through two levels of shell
scripts plus the Makefile.

The binary does now start to run without any linker error, but the application
does not yet work because it cannot load the main module (probably because it
is called 'libradiantcore.so' not 'radiantcore.so').

CMakeLists.txt

@@ -9,6 +9,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED True)
 
 # Build shared libraries by default
 option(BUILD_SHARED_LIBS "Build shared libraries" ON)
+set(CMAKE_INSTALL_RPATH "$ORIGIN/../lib/darkradiant")
 
 # Define GNU-style directory structure by default, and pass directories to the
 # code with defines
@@ -51,3 +52,10 @@ add_subdirectory(libs/module)
 # Main radiant components
 add_subdirectory(radiantcore)
 add_subdirectory(radiant)
+
+# Installation
+install(TARGETS darkradiant math xmlutil scenegraph wxutil module
+        RUNTIME DESTINATION bin
+        LIBRARY DESTINATION lib/darkradiant)
+install(TARGETS radiantcore
+        LIBRARY DESTINATION lib/darkradiant/modules)