try to fix 32-bit test on github actions

for some reasons, this test fails at _installing_ 32-bit dependencies
using the exact same command that actually works in other tests !!?

It's unclear why it fails repeateadly for this test only.
Try another way to install dependencies to fix that.

.github/workflows/generic-dev.yml

@@ -41,7 +41,8 @@ jobs:
     - uses: actions/checkout@v2
     - name: make check on 32-bit
       run: |
-        make libc6install
+        sudo apt update
+        APT_PACKAGES="gcc-multilib" make apt-install
         CFLAGS="-m32 -O1 -fstack-protector" make check V=1
 
   gcc-6-7-libzstd: