message: ensure that STAN_MPI is defined for all tests when MPI is turned on
diff: @@ -25,9 +25,9 @@ path_separator :
  #### MPI TEST #####
  ifdef STAN_MPI
  + GTEST_CXXFLAGS += $(CXXFLAGS_MPI)
  MPI_TESTS := $(patsubst src/%.cpp,%$(EXE),$(shell find src/test -name *mpi_*test.cpp))
  $(MPI_TESTS): LDFLAGS += $(LDFLAGS_MPI)
  - $(MPI_TESTS): CXXFLAGS += $(CXXFLAGS_MPI)
  $(MPI_TESTS): $(LIBMPI)
  endif
  @@ -64,11 +64,11 @@ $(LIBGTEST): $(LIBGTEST)(test/gtest.o)
  test/gtest.o: $(GTEST)/src/gtest-all.cc
  @mkdir -p test
  - $(COMPILE.cc) -O$O $(GTEST_CXXFLAGS) $< $(OUTPUT_OPTION) -Wno-unused-variable
  + $(COMPILE.cc) $< -O$O $(GTEST_CXXFLAGS) $(OUTPUT_OPTION) -Wno-unused-variable
  test/%.o : src/test/%.cpp
  @mkdir -p $(dir $@)
  - $(COMPILE.cc) -O$O $(GTEST_CXXFLAGS) $< $(OUTPUT_OPTION)
  + $(COMPILE.cc) $< -O$O $(GTEST_CXXFLAGS) $(OUTPUT_OPTION)
  ##
  # TEST_TARGETS is the set of all src/test subdirectories excluding src/test.
  