make objects go to build folder, compile in parallel

fortran/Makefile

@@ -2,17 +2,28 @@ BLUE=\033[0;34m
 NC=\033[0m  # No Color
 FC?=flang-new
 COV?=false
+BUILD_DIR=build
+SRC_DIR=src
+SRC_FILES=$(wildcard $(SRC_DIR)/*.f90)
+OBJ_FILES=$(patsubst $(SRC_DIR)/%.f90, $(BUILD_DIR)/%.o, $(SRC_FILES))
+
 
 ifeq ($(FC),ifort)
 opt_args= -Wall -Werror -march=native -qwholeprogram
+else ifeq ($(FC),lfortran)
+opt_args=
 else ifeq ($(FC),nvfortran)
 opt_args= -Wall -Werror -march=native
+else ifneq (,$(findstring flang,$(FC)))
+opt_args= -Werror -march=native -flto
 else
 opt_args= -Wall -Werror -march=native -flto
 endif
 
 ifneq ($(COV),false)
 cov_args= -fprofile-arcs -ftest-coverage -O0
+else ifeq ($(FC),lfortran)
+cov_args=
 else
 cov_args= -O2
 endif
@@ -23,15 +34,19 @@ help:
 	@echo "  $(BLUE)test_auto$(NC)	Run through all Fortran tests (parallel execution not implemented)."
 	@echo "  $(BLUE)clean$(NC)  	Clean up any stray files."
 
+$(BUILD_DIR)/%.o: $(SRC_DIR)/%.f90
+	@mkdir -p $(BUILD_DIR)
+	@$(FC) $(opt_args) $(cov_args) -c $< -o $@ -J$(BUILD_DIR)
+
 .PHONY: test
 test: ../LICENSE
-	@$(FC) $(opt_args) $(cov_args) -c src/*.f90
-	@$(FC) $(opt_args) $(cov_args) *.o test.f90 -o test_runner
+	@$(MAKE) $(OBJ_FILES) $(MFLAGS) -j --no-print-directory
+	@$(FC) $(opt_args) $(cov_args) -J$(BUILD_DIR) build/*.o test.f90 -o test_runner
 	@./test_runner
 
 test_%:
 	@$(MAKE) test $(MFLAGS)
 
 .PHONY: clean
 clean:
-	@rm *.o *.mod test_runner
+	@rm -rf $(BUILD_DIR) test_runner