Add -lm to 2018/hou/Makefile

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

2018/hou/Makefile

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

thanks-for-fixes.md

@@ -1319,6 +1319,12 @@ He also added explicit linking of libm (`-lm`) for systems that do not do this
 Cody added explicit linking of libm (`-lm`) for systems that do not do this
 (linux doesn't seem to but macOS does).
 
+## [2018/hou](2018/hou/prog.c) ([README.md](2018/hou/README.md))
+
+Cody added explicit linking of libm (`-lm`) for systems that do not do this
+(linux doesn't seem to but macOS does).
+
+
 
 ## [2019/ciura](2019/ciura/prog.c) ([README.md](2019/ciura/README.md]))