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

configure.ac

@@ -158,7 +158,7 @@ AC_DEFINE_UNQUOTED([SYSTEM_TYPE],["$ac_cv_build"], [System type])
 AC_SUBST([SYSTEM_TYPE],["$ac_cv_build"])
 #  ----------------------------------------------------------------------
 #  Check for math library
-AC_CHECK_LIB(m, floor)
+AC_SEARCH_LIBS([floor], [m])
 #  ----------------------------------------------------------------------
 # Add basic configure options
 ACX_OPTIONS

tests/Makefile.am

@@ -72,7 +72,7 @@ pio_write_deco2d_LDADD = $(LDADD) $(UUID_C_LIB)
 test_resource_copy_mpi_LDADD = $(LDADD) $(UUID_C_LIB)
 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