Add important note to 1988/spinellis/README.md

One needs to make clobber for this entry to work right! It cannot easily
be added to the Makefile as the rule depends on the source code. This
probably should be fixed.

1988/spinellis/README.md

@@ -13,7 +13,7 @@
 and then type a C program into followed by EOF (usually `^D`, ctrl-d).
 
 [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) made a version (also
-one-line) for clang. See the alternative code section below for how to use.
+one line) for clang. See the alternative code section below for how to use.
 Thank you Cody for your assistance!
 
 ## Try:
@@ -36,6 +36,8 @@ Thank you Cody for your assistance!
 	^D
 	./spinellis
 
+NOTE: you need to make clobber first for this entry to work right.
+
 ## Alternative code:
 
 For clang try the alt code like:
@@ -50,6 +52,7 @@ For clang try the alt code like:
 	./spinellis
 
 
+NOTE: you need to make clobber first for this entry to work right.
 
 ## Judges' comments: