ci: only available dependants

Author: Yishuai Li

.github/workflows/build.yml

@@ -145,7 +145,7 @@ jobs:
       - name: Test dependants
         if: ${{ matrix.os != 'windows-latest' }}
         run: |
-          PACKAGES=$(opam list -s -V --color=never --installable --depends-on cppo,cppo_ocamlbuild | \
+          PACKAGES=$(opam list -a -s -V --color=never --installable --depends-on cppo,cppo_ocamlbuild | \
             awk '{
               if ($0 ~ /^cppo_ocamlbuild\./) next
               line = $0
@@ -179,7 +179,7 @@ jobs:
       - name: Test dependants on Windows
         if: ${{ matrix.os == 'windows-latest' }}
         run: |
-          $rawPackages = & opam list -s -V --color=never --installable --depends-on cppo,cppo_ocamlbuild
+          $rawPackages = & opam list -a -s -V --color=never --installable --depends-on cppo,cppo_ocamlbuild
           $packageMap = @{}
 
           foreach ($line in $rawPackages) {