Link unit tests through CXX

src/Makefile.am

@@ -12,6 +12,19 @@ check_PROGRAMS = \
 	test-gradient-sample2 \
 	test-gradient-trivial
 
+test_gradient_horrible_SOURCES             = test-gradient-horrible.cc
+test_gradient_horrible_logarithmic_SOURCES = test-gradient-horrible-logarithmic.cc
+test_gradient_identity_SOURCES             = test-gradient-identity.cc
+test_gradient_parabola_SOURCES             = test-gradient-parabola.cc
+test_gradient_sample_SOURCES               = test-gradient-sample.cc
+test_gradient_sample_3d_SOURCES            = test-gradient-sample-3d.cc
+test_gradient_sample_nonsmooth_SOURCES     = test-gradient-sample-nonsmooth.cc
+test_gradient_sample_steep_SOURCES         = test-gradient-sample-steep.cc
+test_gradient_sample_steep2_SOURCES        = test-gradient-sample-steep2.cc
+test_gradient_sample_verysteep_SOURCES     = test-gradient-sample-verysteep.cc
+test_gradient_sample2_SOURCES              = test-gradient-sample2.cc
+test_gradient_trivial_SOURCES              = test-gradient-trivial.cc
+
 bin_PROGRAMS = \
 	one-body-sample-2D \
 	one-body-sample-3D