FIXUP: Do not link to -lm if it is not required.

tests/Makefile.am

@@ -60,7 +60,7 @@ pio_write_deco2d_LDADD = $(LDADD)
 test_resource_copy_mpi_LDADD = $(LDADD)
 endif
 
-LDADD = ../src/libcdi.la -lm
+LDADD = ../src/libcdi.la
 AM_CPPFLAGS = -I$(top_srcdir)/src
 #
 EXTRA_DIST = test_cdf_write.c test_cdf_read.c test_cksum_base