build: Replace make protoc with for loop to return an error (aqua…

…security#1655)

Find the `*.proto` files and run in a `for loop` to run `protoc`
for each file in a separated command. If fail, `|| exit` will exit
with the returned error.

The POSIX standard specifies that the return status of `find` is 0
unless an error occurred while traversing the directories;
the return status of executed commands doesn't enter into it.

To overcome this limitation, the `-exec ... +` pattern could be used
From the docs (https://man7.org/linux/man-pages/man1/find.1.html):
"If any invocation with the `+' form returns a non-zero
value as exit status, then find returns a non-zero exit
status."

But as well, "This variant of the -exec action runs the specified command
on the selected files, but the command line is built by appending each selected
file name at the end;"

Unfortunately, at the moment `protoc-gen-twirp` plugin doesn't
support multiple files from different packages when the `go_package` option
is explicitly mentioned.
https://github.com/twitchtv/twirp/blob/main/protoc-gen-twirp/generator.go#L181-L185

Signed-off-by: Yuval Goldberg <[email protected]>

Makefile

@@ -58,7 +58,9 @@ protoc:
 	docker run --rm -it -v ${PWD}:/app -w /app trivy-protoc make _$@
 
 _protoc:
-	find ./rpc/ -name "*.proto" -type f -exec protoc --twirp_out=. --twirp_opt=paths=source_relative --go_out=. --go_opt=paths=source_relative {} \;
+	for path in `find ./rpc/ -name "*.proto" -type f`; do \
+		protoc --twirp_out=. --twirp_opt=paths=source_relative --go_out=. --go_opt=paths=source_relative $${path} || exit; \
+	done
 
 .PHONY: install
 install: