fix ENABLE_SBT_THIN_CLIENT and refactor run_main

Chipyard doesn't use run_main so define it here.  Also make it revert to using
run_scala_main when ENABLE_SBT_THIN_CLIENT

sim/Makefile

@@ -65,8 +65,6 @@ SBT ?= java $(JAVA_OPTS) -jar $(rocketchip_dir)/sbt-launch.jar $(SBT_OPTS) $(SBT
 define run_scala_main
 	cd $(base_dir) && $(SBT) ";project $(1); runMain $(2) $(3)"
 endef
-# recipes for generator and gg using sbt are calls out to FAT_JAR instead of SBT
-run_main = cd $(base_dir) && java $(JAVA_ARGS) -cp $(FAT_JAR) $(2) $(3)
 
 ##############################################################################
 # SBT Server Setup (start server / rebuild proj. defs. if SBT_SOURCES change)
@@ -96,6 +94,15 @@ include $(base_dir)/variables.mk
 include $(base_dir)/common.mk
 endif
 
+ifdef ENABLE_SBT_THIN_CLIENT
+    # when asking to use SBT_THIN_CLIENT (typically for faster turnaround on scala tests)
+    # continue to use SBT for main class invocations of the generator and goldengate
+    run_main = run_scala_main
+else
+    # recipes for generator and gg using sbt are calls out to FAT_JAR instead of SBT
+    run_main = cd $(base_dir) && java $(JAVA_OPTS) -cp $(FAT_JAR) $(2) $(3)
+endif
+
 # Include target-specific sources and input generation recipes
 include $(TARGET_PROJECT_MAKEFRAG)
 

sim/target-agnostic.mk

@@ -89,7 +89,7 @@ conf: $(fame_annos) $(FAT_JAR)
 	mkdir -p $(GENERATED_DIR)
 	# Runtime configuration generator must run under SBT currently; When
 	# launched via bloop some Console input and output is lost.
-	cd $(base_dir) && java $(JAVA_ARGS) -cp $(FAT_JAR) midas.stage.RuntimeConfigGeneratorMain \
+	cd $(base_dir) && java $(JAVA_OPTS) -cp $(FAT_JAR) midas.stage.RuntimeConfigGeneratorMain \
 		-td $(GENERATED_DIR) \
 		-faf $(fame_annos) \
 		-ggcp $(PLATFORM_CONFIG_PACKAGE) \
@@ -245,8 +245,13 @@ fpga: $(fpga_v) $(base_dir)/scripts/checkpoints/$(name_tuple)
 #  that look like "make: Nothing to be done for `replace-rtl'."
 .PHONY: gen-replace-rtl-script
 gen-replace-rtl-script: $(PRE_ELABORATION_TARGETS) | $(GENERATED_DIR)
+ifdef ENABLE_SBT_THIN_CLIENT
+	@echo "Use of ENABLE_SBT_THIN_CLIENT is inconsistent with the purpose of 'gen-replace-rtl-script'. Aborting."
+	@exit 1
+else
 	$(MAKE) replace-rtl -n  --no-print-directory $(addprefix --assume-new=, $(PRE_ELABORATION_TARGETS)) > $(GENERATED_DIR)/replace-rtl.sh
 	$(firesim_base_dir)/../scripts/repo_state_summary.sh > $(GENERATED_DIR)/repo_state
+endif
 
 
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