Add -lm to 2013/morgan1/Makefile

Not all systems implicitly link in libm so this is necessary for those
systems.

2013/morgan1/Makefile

@@ -73,7 +73,7 @@ CFLAGS= ${CSTD} ${CWARN} ${ARCH} ${CDEFINE} ${CINCLUDE} ${OPT}
 
 # Libraries needed to build
 #
-LIBS= -L ${X11_LIBDIR} -lX11
+LIBS= -L ${X11_LIBDIR} -lX11 -lm
 
 # C compiler to use
 #

thanks-for-fixes.md

@@ -1294,6 +1294,11 @@ removed from SDL2 so the Makefile has to use `sdl-config` and not `sdl2-config`.
 This means that to be strictly technical, the removal of `localtime()` is not
 necessary but this change was left in place anyway.
 
+## [2013/morgan1](2013/morgan1/morgan1.c) ([README.md](2013/morgan1/README.md))
+
+Cody added explicit linking of libm (`-lm`) as not all systems do this
+implicitly (linux doesn't seem to but macOS does).
+
 
 ## [2014/maffiodo1](2014/maffiodo1/maffiodo1.c) ([README.md](2014/maffiodo1/README.md]))