Enable warning flags on Mac builds of MFEM

CONTRIBUTING.md

@@ -0,0 +1,12 @@
+# Welcome to the MFEM GitHub actions repository
+
+The github actions in this repo are used in several projects.
+
+The projects mentioned in [README.md](README.md) are considered critical users of this repo. When introducing a change in this repo, 
+care should be taken to check that those will not break the CI process of the critical users.
+
+The verification process is as follow:
+- Create a branch with the changes in the GitHub actions. Push this branch to the GitHub repo.
+- Create branches out of current master in the projects mentioned in [README.md](README.md). In those branches, point the GitHub actions to your new branch.
+- Create pull requests, marked as `do-not-merge` in the projects so that CI is triggered with your new changes.
+- Once working, submit a PR to the GitHub actions repo.

README.md

@@ -0,0 +1,16 @@
+# Welcome to the MFEM GitHub actions repository
+
+The goal of this repository is to gather the GitHub actions used by MFEM, projects related to MFEM, or any other project 
+interested in using them. Keeping these in one repo avoids duplicating and maintaining several copies of similar actions.
+
+Projects using these actions:
+- [mfem/mfem](https://github.com/mfem/mfem)
+- [glvis/glvis](https://github.com/glvis/glvis)
+- [ceed/laghos](https://github.com/ceed/laghos)
+- [ceed/remhos](https://github.com/ceed/remhos)
+
+Description of the actions:
+- [`build-hypre`](build-hypre/action.yml) will download and build hypre with some degree of configuration, dictated by mfem typical usage.
+- [`build-metis`](build-metis/action.yml) will download and build metis with some degree of configuration, dictated by mfem typical usage.
+- [`build-mfem`](build-mfem/action.yml) will download and build mfem. This one has more configuration options, since we want to enable building various mfem configurations. It is also intended to build mfem both as the main project (in mfem CI) or as a dependency, in which case one can control what repo and branch to use.
+- [`upload-coverage`](upload-coverage/action.yml) is a standard action to upload coverage information to codecov.

build-mfem/action.yml

@@ -85,9 +85,10 @@ runs:
         if [[ ${{ inputs.target }} == 'dbg' ]]; then
           DEBUG="YES";
           BUILD_TYPE="Debug";
-          if [[ ${{ inputs.os }} == 'ubuntu-18.04' ]]; then
-            CPPFLAGS+=" -pedantic -Wall -Werror";
-          fi
+        fi
+        if [[ ${{ inputs.os }} != 'ubuntu-18.04' || \
+              ${{ inputs.target }} == 'dbg' ]]; then
+          CPPFLAGS+=" -pedantic -Wall -Werror";
         fi
         echo "[STATUS] DEBUG: ${DEBUG}"
         echo "[STATUS] BUILD_TYPE: ${BUILD_TYPE}"