CI config: Specify RepositoryBranch when building inside a docker container

Author: natemcmaster

.azure/pipelines/ci.yml

@@ -258,7 +258,7 @@ jobs:
     jobDisplayName: "Build: Linux Musl x64"
     agentOs: Linux
     buildScript: ./dockerbuild.sh alpine
-    buildArgs: --ci --pack --all -e KOREBUILD_SKIP_INSTALL_NETFX=0 --arch x64 --os-name linux-musl --no-build-nodejs --no-build-java
+    buildArgs: --ci --pack --all -e KOREBUILD_SKIP_INSTALL_NETFX=0 --arch x64 --os-name linux-musl --no-build-nodejs --no-build-java -p:RepositoryBranch=$(Build.SourceBranchName)
     installNodeJs: false
     afterBuild:
     # Remove packages that are not rid-specific.