ensure bash is installed and used for custom scripts

Dockerfile

@@ -22,7 +22,7 @@ ENV LHCI_BASE_DIR=/drone/src \
 
 ADD overlay/ /
 
-RUN apt-get update && apt-get install -y git curl wget gnupg jq && \
+RUN apt-get update && apt-get install -y git curl wget gnupg jq bash && \
     curl -SsL -o /usr/local/bin/yq "https://github.com/mikefarah/yq/releases/download/${YQ_VERSION}/yq_linux_amd64" && \
     chmod 755 /usr/local/bin/yq && \
     wget -qO - "https://dl-ssl.google.com/linux/linux_signing_key.pub" | apt-key add - && \

overlay/usr/bin/lhci

@@ -1,4 +1,4 @@
-#!/usr/bin/env sh
+#!/usr/bin/env bash
 set -eo pipefail
 
 CONFIG="${LHCI_BASE_DIR%/}/.lighthouserc.yml"

overlay/usr/bin/lhci-official

@@ -1,4 +1,4 @@
-#!/usr/bin/env sh
+#!/usr/bin/env bash
 set -eo pipefail
 
 exec /usr/local/bin/lhci "$@"