Remove alpine 3.8 and cleanup 3.11 (#451)

Co-authored-by: Aditya Patwardhan <Aditya Patwardhan>

Author: adityapatwardhan

release/lts/alpine38/dependabot/Dockerfile

@@ -3,11 +3,7 @@
 
 # Docker image file that describes an Alpine3.11 image with PowerShell installed from .tar.gz file(s)
 
-# Define arg(s) needed for the From statement
-ARG fromTag=3.11
-ARG imageRepo=alpine
-
-FROM ${imageRepo}:${fromTag} AS installer-env
+FROM alpine:3.11 AS installer-env
 
 # Define Args for the needed to add the package
 ARG PS_VERSION=7.0.0-preview.1
@@ -28,9 +24,7 @@ RUN mkdir -p ${PS_INSTALL_FOLDER}
 RUN tar zxf /tmp/linux.tar.gz -C ${PS_INSTALL_FOLDER} -v
 
 # Start a new stage so we lose all the tar.gz layers from the final image
-FROM ${imageRepo}:${fromTag}
-
-ARG fromTag=3.11
+FROM alpine:3.11
 
 # Copy only the files we need from the previous stage
 COPY --from=installer-env ["/opt/microsoft/powershell", "/opt/microsoft/powershell"]
@@ -45,7 +39,7 @@ ENV PS_INSTALL_FOLDER=/opt/microsoft/powershell/$PS_INSTALL_VERSION \
     LANG=en_US.UTF-8 \
     # set a fixed location for the Module analysis cache
     PSModuleAnalysisCachePath=/var/cache/microsoft/powershell/PSModuleAnalysisCache/ModuleAnalysisCache \
-    POWERSHELL_DISTRIBUTION_CHANNEL=PSDocker-Alpine-${fromTag}
+    POWERSHELL_DISTRIBUTION_CHANNEL=PSDocker-Alpine-3.11
 
 # Install dotnet dependencies and ca-certificates
 RUN apk add --no-cache \

release/lts/alpine38/docker/Dockerfile

@@ -7,6 +7,9 @@
         "#psversion#-alpine-#tag#",
         "preview-alpine-#shorttag#"
     ],
+    "shortTags": [
+        {"Tag": "3.11"}
+    ],
     "SkipGssNtlmSspTests": true,
     "SubImage": "test-deps",
     "TestProperties": {