Fix @goyacc invocation (#14324)

goyacc is installed using 'install-goyacc' and ends up in GOPATH/bin.
GOPATH isn't usually part of standard PATH, so when make tries to run goyacc it fails, unless PATH includes GOPATH/bin.
Other Go tools, like golangci-lint, are also installed via go install into GOPATH/bin but they run correctly because make invocations for them use FIRST_GOPATH viriable to use full path.
Call goyacc using FIRST_GOPATH/bin as well so it works without GOPATH being included in PATH.

Signed-off-by: Lukasz Mierzwa <lukasz@cloudflare.com>

Makefile

@@ -91,7 +91,7 @@ endif
 
 promql/parser/generated_parser.y.go: promql/parser/generated_parser.y
 	@echo ">> running goyacc to generate the .go file."
-	@goyacc -l -o promql/parser/generated_parser.y.go promql/parser/generated_parser.y
+	@$(FIRST_GOPATH)/bin/goyacc -l -o promql/parser/generated_parser.y.go promql/parser/generated_parser.y
 
 .PHONY: clean-parser
 clean-parser: