try to fix CI

.github/workflows/main.yml

@@ -18,6 +18,7 @@ jobs:
               #- windows-latest
         ocaml-compiler:
             - '4.08.x'
+            - '4.12.x'
             - '4.14.x'
             - '5.0.x'
 
@@ -33,7 +34,10 @@ jobs:
 
       - run: opam install -t trace trace-tef trace-fuchsia --deps-only
       - run: opam install ppx_trace --deps-only # no tests
-      - run: opam exec -- dune build '@install' -p trace,trace-tef,trace-fuchsia,ppx_trace
+        if: matrix.ocaml-compiler != '4.08.x'
+      - run: opam exec -- dune build '@install' -p trace,trace-tef,trace-fuchsia
+      - run: opam exec -- dune build '@install' -p ppx_trace
+        if: matrix.ocaml-compiler != '4.08.x'
       - run: opam exec -- dune runtest -p trace
       - run: opam install trace
       - run: opam exec -- dune runtest -p trace-tef trace-fuchsia

ppx_trace.opam

@@ -5,12 +5,12 @@ synopsis: "A ppx-based preprocessor for trace"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
 license: "MIT"
-tags: ["trace" "tracing" "observability" "profiling" "ppx"]
+tags: ["trace" "ppx"]
 homepage: "https://github.com/c-cube/ocaml-trace"
 bug-reports: "https://github.com/c-cube/ocaml-trace/issues"
 depends: [
   "ocaml" {>= "4.12"}
-  "ppxlib" {>= "0.28"}
+  "ppxlib" {>= "0.25"}
   "trace" {= version}
   "trace-tef" {= version & with-test}
   "dune" {>= "2.9"}

trace-tef.opam

@@ -6,7 +6,7 @@ synopsis:
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
 license: "MIT"
-tags: ["trace" "tracing" "catapult"]
+tags: ["trace" "tracing" "catapult" "TEF" "chrome-format"]
 homepage: "https://github.com/c-cube/ocaml-trace"
 bug-reports: "https://github.com/c-cube/ocaml-trace/issues"
 depends: [