avoid link failed on unit test for mac os

paddle/math/tests/test_CpuGpuVector.cpp

@@ -84,4 +84,10 @@ int main(int argc, char** argv) {
   return ret;
 }
 
+#else
+
+int main(int argc, char const* argv[]) {
+    return 0;
+}
+
 #endif

paddle/math/tests/test_matrixCompare.cpp

@@ -1851,5 +1851,10 @@ int main(int argc, char** argv) {
   initMain(argc, argv);
   return RUN_ALL_TESTS();
 }
+#else
+
+int main(int argc, char const* argv[]) {
+    return 0;
+}
 
 #endif

paddle/math/tests/test_perturbation.cpp

@@ -254,4 +254,10 @@ int main(int argc, char** argv) {
   return RUN_ALL_TESTS();
 }
 
+#else
+
+int main(int argc, char const* argv[]) {
+    return 0;
+}
+
 #endif

paddle/math/tests/test_sparseMatrixCompare.cpp

@@ -178,4 +178,10 @@ int main(int argc, char** argv) {
   return ret;
 }
 
+#else
+
+int main(int argc, char const* argv[]) {
+    return 0;
+}
+
 #endif