cleanup: Generate proto with go generate only if proto tag is provided

Avoids generating proto files unless explicitly requested.

As per this it's now an error if the generation script is called during
package build.

.github/workflows/qa.yaml

@@ -45,6 +45,12 @@ jobs:
         run: |
           set -eu
           go run -tags pam_binary_cli ./pam login --exec-debug
+      - name: Generate Proto files
+        run: |
+          set -eu
+          find -name "*.pb.go" -delete -print
+          go generate -x -tags proto ./...
+          find -name "*.pb.go"
       - name: Generate PAM module
         run: |
           set -eu

generate.go → generate_proto.go

@@ -1,4 +1,4 @@
-//go:build generate
+//go:build generate && proto
 
 //go:generate tools/generate-proto.sh --with-grpc authd.proto
 

internal/daemon/testdata/grpctestservice/generate.go → internal/daemon/testdata/grpctestservice/generate_proto.go

@@ -1,4 +1,4 @@
-//go:build generate
+//go:build generate && proto
 
 //go:generate ../../../../tools/generate-proto.sh --with-grpc grpctestservice.proto
 

pam/internal/gdm/generate_proto.go

@@ -0,0 +1,5 @@
+//go:build generate && proto
+
+//go:generate ../../../tools/generate-proto.sh -I../../.. -I../proto gdm.proto
+
+package gdm

pam/internal/gdm/protocol.go

@@ -1,5 +1,3 @@
-//go:generate ../../../tools/generate-proto.sh -I../../.. -I../proto gdm.proto
-
 // Package gdm is the package for the GDM pam module handing.
 package gdm
 

pam/internal/proto/generate.go → pam/internal/proto/generate_proto.go

@@ -1,4 +1,4 @@
-//go:build generate
+//go:build generate && proto
 
 //go:generate ../../../tools/generate-proto.sh pam.proto
 

tools/generate-proto.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 
 if [ -v DEB_HOST_GNU_TYPE ]; then
     echo "Proto files should not be regenerated during package building"
-    exit 0
+    exit 1
 fi
 
 # TODO: Watch https://github.com/protocolbuffers/protobuf for any changes on the