Fix prefix variable name typo. (Fixed upstream 2006-01-16.)

Fix method of linking with CoreServices for macOS Big Sur v11 and later.
https://sourceforge.net/p/fondu/bugs/12/
--- Makefile.in.orig	2006-01-02 17:19:58.000000000 -0600
+++ Makefile.in	2023-11-16 04:03:07.000000000 -0600
@@ -1,6 +1,6 @@
 # @configure_input@
 
-wilprefix = @prefix@
+prefix = @prefix@
 exec_prefix = @exec_prefix@
 bindir = @bindir@
 
@@ -10,7 +10,7 @@
 HOST= @HOST@
 
 
-DARWIN_CORE = $(if $(findstring apple-darwin,$(HOST)),/System/Library/Frameworks/CoreServices.framework/CoreServices,)
+DARWIN_CORE = $(if $(findstring apple-darwin,$(HOST)),-framework CoreServices,)
 
 WFLAGS = -Wmissing-prototypes -Wunused -Wimplicit -Wreturn-type -Wparentheses -pedantic
 CFLAGS = -g $(WFLAGS)