[CI] Fix alpine builds (WebAssembly#4284)

MaxGraey · web-flow · commit 446d97617f02 · 2021-10-28T14:16:28.000-07:00
It seems that now alpine requires pip3.
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -171,7 +171,7 @@ jobs:
     - name: install packages
       run: |
         ./alpine.sh apk update
-        ./alpine.sh apk add build-base cmake git python3 clang ninja
+        ./alpine.sh apk add build-base cmake git python3 py3-pip clang ninja
 
     - name: install python dev dependencies
       run: ./alpine.sh pip3 install -r requirements-dev.txt
