(Torturing the Scanner): Don't invoke "cc a.c b.c

-o c"; the HP-UX 11i C compiler chatters during compilation.
Instead, invoke "cc -c a.c -o a.o; cc -c b.c -o b.o; cc a.o b.o -o c".

tests/input.at

@@ -202,7 +202,9 @@ main (void)
 ]])
 
 AT_CHECK([bison -d -v -o input.c input.y])
-AT_COMPILE([input], [input.c main.c])
+AT_COMPILE([input.o], [-c input.c])
+AT_COMPILE([main.o], [-c main.c])
+AT_COMPILE([input], [input.o main.o])
 AT_PARSER_CHECK([./input], 0,
 [[[@<:@],
 ]])