CMake: put all binaries into a single location.

Shouldn't really make any difference, since pybind redirects all
libraries anyway. But since other projects set this globally, we need to
ensure this won't break anything.

CMakeLists.txt

@@ -40,5 +40,36 @@ option(WITH_PYTHON "Build Python bindings" OFF)
 
 set(MAGNUMBINDINGS_CMAKE_MODULE_INSTALL_DIR share/cmake/MagnumBindings)
 
+# A single output location. After a decade of saying NO THIS IS A NON-SOLUTION
+# TO A NON-PROBLEM I reconsidered my views and enabled this, because:
+#
+# - On Windows (which don't have RPATH), this makes test execution finally
+#   possible without having to install all the stuff first (including the
+#   test-only libs, which is ugh).
+# - With CMake subprojects, this makes it finally possible to use dynamic
+#   plugins directly from the build dir (again without installing anything) ---
+#   all plugins are put into the same place, so PluginManager has a single
+#   place to look into; and thanks to the dynamic libraries being there as
+#   well, this location can be automagically detected as relative to
+#   Directory::libraryLocation().
+# - Thanks to the $<CONFIG> being part of the output path, you are always sure
+#   you never accidentally mix up debug/release libraries when switching
+#   CMAKE_BUILD_TYPE in an existing build dir.
+#
+# The runtime location is set to CMAKE_BINARY_DIR and not PROJECT_BINARY_DIR
+# because have one runtime location per CMake subproject would not solve much
+# either. If the user already provides CMAKE_RUNTIME_OUTPUT_DIRECTORY (even
+# empty), it's respected and nothing is being done.
+#
+# Explicitly using a generator expression to ensure plugins are added to e.g.
+# <CONFIG>/lib/magnum/importers/ instead of lib/magnum/importers/<CONFIG>. Also
+# adding this to cache, making superprojects pick that up implicitly as well,
+# without forcing them to explicitly mirror this setting.
+if(NOT DEFINED CMAKE_RUNTIME_OUTPUT_DIRECTORY)
+    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/$<CONFIG>/bin CACHE PATH "" FORCE)
+    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/$<CONFIG>/lib CACHE PATH "" FORCE)
+    set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/$<CONFIG>/lib CACHE PATH "" FORCE)
+endif()
+
 add_subdirectory(modules)
 add_subdirectory(src)