pam: Introduce pam_debug build tag to generate debug libraries

When using this tag on `go build` or `go generate` we:
 - Add more debug symbols to built libraries
 - Enable pedantic checks on data structures used by GDM proto

To achieve this, add a further generate_debug.go file that is only
used when the `pam_debug` tag is used, this now also builds the gdm
code with the `pam_gdm_debug` build tag that implies enabling by
default some checks that are not enabled by default.

Update CI job to ensure this works.

.github/workflows/qa.yaml

@@ -35,6 +35,20 @@ jobs:
         run: |
           set -eu
           go build -tags withexamplebroker ./cmd/authd
+      - name: Generate PAM module
+        run: |
+          set -eu
+          find pam -name '*.so' -print -delete
+          go generate -C pam -x
+          test -e pam/pam_authd.so
+          test -e pam/go-loader/pam_go_loader.so
+      - name: Generate PAM module with pam_debug tag
+        run: |
+          set -eu
+          find pam -name '*.so' -print -delete
+          go generate -C pam -x -tags pam_debug
+          test -e pam/pam_authd.so
+          test -e pam/go-loader/pam_go_loader.so
 
   rust-sanity:
     name: "Rust: Code sanity"

pam/gdm/debug.go

@@ -0,0 +1,8 @@
+//go:build pam_gdm_debug
+
+package gdm
+
+func init() {
+	checkMembersFunc = checkMembersDebug
+	validateJSONFunc = validateJSONDebug
+}

pam/generate.go

@@ -1,5 +1,5 @@
-//go:build generate
+//go:build generate && !pam_debug
 
-//go:generate ./generate.sh -tags !pam_binary_cli
+//go:generate ./generate.sh -tags "!pam_binary_cli && !pam_debug"
 
 package main

pam/generate_debug.go

@@ -0,0 +1,5 @@
+//go:build generate && pam_debug
+
+//go:generate env CFLAGS=-g3 CGO_CFLAGS=-g3 ./generate.sh -tags "!pam_binary_cli && pam_debug" -build-tags pam_gdm_debug -output pam_module_debug.go
+
+package main