[Makefile] Added a basic manifest target to hash rtl/.v files

Makefile

diff --git a/Makefile b/Makefile
index 0071b95..60af834 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-# cannot commit files larger than 100 MB to GitHub 
+# cannot commit files larger than 100 MB to GitHub
 FILE_SIZE_LIMIT_MB = 100
 LARGE_FILES := $(shell find ./gds -type f -name "*.gds")
 LARGE_FILES += $(shell find . -type f -size +$(FILE_SIZE_LIMIT_MB)M -not -path "./.git/*" -not -path "./gds/*" -not -path "./openlane/*")
@@ -8,7 +8,6 @@
 ARCHIVES := $(shell find . -type f -name "*.gz")
 ARCHIVE_SOURCES := $(basename $(ARCHIVES))
 
-
 # PDK setup configs
 THREADS ?= $(shell nproc)
 STD_CELL_LIBRARY ?= sky130_fd_sc_hd
@@ -134,6 +133,11 @@
 		$(MAKE) && \
 		$(MAKE) install-local
 
+.RECIPE: manifest
+manifest:
+	cd verilog/rtl/ && \
+	find * -type f ! -name "user_*.v" ! -name "README" ! -name "defines.v" -exec shasum {} \; > manifest
+
 check-env:
 ifndef PDK_ROOT
 	$(error PDK_ROOT is undefined, please export it before running make)