chore(ci): add envsubst to centos:7 build flow

Author: Akash Satheesan

.github/workflows/ci.yaml

@@ -149,9 +149,12 @@ jobs:
           yum install -y epel-release centos-release-scl
           yum install -y devtoolset-9-{make,gcc,gcc-c++} jq rsync
 
-      - name: Install nfpm
+      - name: Install nfpm and envsubst
         run: |
           curl -sfL https://install.goreleaser.com/github.com/goreleaser/nfpm.sh | sh -s -- -b ~/.local/bin v2.3.1
+          curl -L https://github.com/a8m/envsubst/releases/download/v1.1.0/envsubst-`uname -s`-`uname -m` -o envsubst
+          chmod +x envsubst
+          mv envsubst ~/.local/bin
           echo "$HOME/.local/bin" >> $GITHUB_PATH
 
       - name: Install yarn