The Xlib demos were fixed to use $(X11_LIBS) so that configure could
detect the proper directory to link the library from, but this broke
the non-autoconf builds. Give X11_LIBS a default value to fallback on.
# Program dependencies - specific GL/glut libraries added in Makefiles
APP_LIB_DEPS = -lm
# Program dependencies - specific GL/glut libraries added in Makefiles
APP_LIB_DEPS = -lm
# Installation directories (for make install)
INSTALL_DIR = /usr/local
# Installation directories (for make install)
INSTALL_DIR = /usr/local