utils/Makefile: Use LOADLIBES instead of LDFLAGS to link the math library.

Matthew Pirocchi <mrpirocchi@email.wm.edu>, via John Ousterhout
<ouster@cs.stanford.edu> reports that this fixes a problem on his system.

src/utils/Makefile

@@ -2,7 +2,7 @@ all: setitimer-helper squish-pty squish-unix
 
 CC = gcc
 CFLAGS = -Wall -W
-LDFLAGS = -lm
+LOADLIBES = -lm
 setitimer-helper: setitimer-helper.o
 squish-pty: squish-pty.o
 squish-unix: squish-unix.o