drop manifest.txt support favoring diff and git-sig

Makefile

@@ -107,7 +107,7 @@ reproduce: toolchain-clean
 	mkdir -p $(OUT_DIR)
 	cp $(DIST_DIR)/release.env $(OUT_DIR)/release.env
 	$(MAKE) TARGET=$(TARGET) VERSION=$(VERSION)
-	diff -q $(OUT_DIR)/manifest.txt $(DIST_DIR)/manifest.txt \
+	diff -q $(OUT_DIR) $(DIST_DIR) \
 	&& echo "Success: $(OUT_DIR) and $(DIST_DIR) are identical"
 
 .PHONY: $(DIST_DIR)
@@ -164,15 +164,6 @@ $(OUT_DIR)/release.env: | $(OUT_DIR)
 	echo 'GIT_KEY=$(GIT_KEY)'             >> $(OUT_DIR)/release.env
 	echo 'GIT_TIMESTAMP=$(GIT_TIMESTAMP)' >> $(OUT_DIR)/release.env
 
-$(OUT_DIR)/manifest.txt: $(wildcard $(OUT_DIR)/*)
-	find -L $(OUT_DIR) \
-		-type f \
-		-not -path "$(OUT_DIR)/manifest.txt" \
-		-exec openssl sha256 -r {} \; \
-	| sed -e 's/ \*out\// /g' -e 's/ \.\// /g' \
-	| LC_ALL=C sort -k2 \
-	> $@
-
 check_executables := $(foreach exec,$(executables),\$(if \
 	$(shell which $(exec)),some string,$(error "No $(exec) in PATH")))
 

README.md

@@ -80,21 +80,6 @@ us as desired.
       ")
     ```
 
-7. Define a release target for your project depending on manifest.txt
-
-    ```
-    .PHONY: release
-    release: $(OUT_DIR)/hello $(OUT_DIR)/manifest.txt
-    	mkdir -p $(RELEASE_DIR)
-    	cp $(OUT_DIR)/hello $(RELEASE_DIR)/hello
-    	cp $(OUT_DIR)/release.env $(RELEASE_DIR)/release.env
-    	cp $(OUT_DIR)/manifest.txt $(RELEASE_DIR)/manifest.txt
-    ```
-
-    Note that manifest.txt is optional, but it makes for an ideal single file
-    to sign if a release will contain more than one artifact.
-
-
 ## Usage ##
 
 ### Build a new release