.github/workflows: add pkgcheck and repoman checks

Lets see if this will work like this

Thanks to the ::science overlay

Bug: https://github.com/gentoo/guru/issues/16

Package-Manager: Portage-3.0.12, Repoman-3.0.2
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@riseup.net>

.github/workflows/pkgcheck.yml

@@ -0,0 +1,31 @@
+name: pkgcheck
+
+on:
+  push:
+    branches: [ dev ]
+  pull_request:
+    branches: [ dev ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python 3.9
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.9
+    - name: Install pkgcheck
+      run: |
+        python -m pip install --upgrade pip
+        pip install pkgcheck
+    - name: Setup master gentoo repository
+      run: |
+        sudo mkdir -p /var/db/repos/gentoo /etc/portage /var/cache/distfiles
+        wget -qO - "https://github.com/gentoo-mirror/gentoo/archive/master.tar.gz" | sudo tar xz -C /var/db/repos/gentoo --strip-components=1
+        sudo wget "https://www.gentoo.org/dtd/metadata.dtd" -O /var/cache/distfiles/metadata.dtd
+        sudo wget "https://gitweb.gentoo.org/proj/portage.git/plain/cnf/repos.conf" -O /etc/portage/repos.conf
+        sudo ln -s /var/db/repos/gentoo/profiles/default/linux/amd64/17.0 /etc/portage/make.profile        
+    - name: Test with pkgcheck
+      run: |
+        pkgcheck scan --exit --check=-RedundantVersionCheck,-VisibilityCheck