Add note reminding folks to remove config.cache after changing

environmental variables.

INSTALL

@@ -145,6 +145,9 @@ The configure script will also use your environmental
 variables for determining compiler/linker options.   This can
 be used to manual specify features and compilation options.
 
+NOTE: If you change environment setting, be sure to remove
+	any config.cache before running ./configure.
+
 Supported Environmental Variables
 	CC			C compiler		(cc, egcc)
 	CFLAGS		C flags			(-ansi)