Enable checking out caravel or caravel-lite to specific commit

Defaults to master and main respectively

Makefile

diff --git a/Makefile b/Makefile
index 16104a7..f576dda 100644
--- a/Makefile
+++ b/Makefile
@@ -23,9 +23,11 @@
 ifeq ($(CARAVEL_LITE),1) 
 	CARAVEL_NAME := caravel-lite
 	CARAVEL_REPO := https://github.com/efabless/caravel-lite 
+	CARAVEL_COMMIT := main
 else
 	CARAVEL_NAME := caravel
 	CARAVEL_REPO := https://github.com/efabless/caravel 
+	CARAVEL_COMMIT := master
 endif
 
 # Install caravel as submodule, (1): submodule, (0): clone
@@ -74,10 +76,12 @@
 	@echo "Installing $(CARAVEL_NAME) as a submodule.."
 	@if [ ! -d $(CARAVEL_ROOT) ]; then git submodule add --name $(CARAVEL_NAME) $(CARAVEL_REPO) $(CARAVEL_ROOT); fi
 	@git submodule update --init
+	@cd $(CARAVEL_ROOT); git checkout $(CARAVEL_HASH)
 	$(MAKE) simlink
 else
 	@echo "Installing $(CARAVEL_NAME).."
 	@git clone $(CARAVEL_REPO) $(CARAVEL_ROOT)
+	@cd $(CARAVEL_ROOT); git checkout $(CARAVEL_HASH)
 endif
 
 # Create symbolic links to caravel's main files