diff --git a/.dockerignore b/.dockerignore
index 5993950c47a..67448e52074 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,4 +1,3 @@
-**/.git
-docker
-build
+.git
+build*
 Dockerfile
diff --git a/docker/Dockerfile.runtime b/docker/Dockerfile.runtime
index 05fff5db733..03521158f8d 100644
--- a/docker/Dockerfile.runtime
+++ b/docker/Dockerfile.runtime
@@ -4,7 +4,7 @@
 # instead use etc/DockerHelper.sh
 
 ARG copyImage=openroad/centos7-builder:latest
-# need to use the line below as the --from does not accept an ARG
+# need to use the line below as the "COPY --from" does not accept an ARG
 FROM $copyImage AS copyfrom
 
 ARG fromImage=centos:centos7
diff --git a/docker/test_wrapper.sh b/docker/test_wrapper.sh
new file mode 100755
index 00000000000..76de969a7e8
--- /dev/null
+++ b/docker/test_wrapper.sh
@@ -0,0 +1,22 @@
+#!/bin/bash
+
+set -eo pipefail
+
+cd "$(dirname $(readlink -f $0))/../"
+
+compiler=${1:-gcc}
+if [[ "${compiler}" == "gcc" ]]; then
+    if [[ -f "/opt/rh/devtoolset-8/enable" ]]; then
+        source /opt/rh/devtoolset-8/enable
+    fi
+    shift 1
+fi
+
+if [[ "${compiler}" == "clang" ]]; then
+    if [[ -f "/opt/rh/llvm-toolset-7.0/enable" ]]; then
+        source /opt/rh/llvm-toolset-7.0/enable
+    fi
+    shift 1
+fi
+
+eval "${@}"
diff --git a/etc/Build.sh b/etc/Build.sh
index 9b54fc1e587..0adb6ba6ced 100755
--- a/etc/Build.sh
+++ b/etc/Build.sh
@@ -4,9 +4,13 @@ set -eo pipefail
 
 cd "$(dirname $(readlink -f $0))/../"
 
+# default values, can be overwritten by cmdline args
 buildDir="build"
 numThreads="$(nproc)"
 cmakeOptions=()
+cleanBefore=no
+keepLog=no
+compiler=gcc
 
 _help() {
     cat <<EOF
@@ -77,7 +81,7 @@ while [ "$#" -gt 0 ]; do
     shift 1
 done
 
-case "${compiler:-gcc}" in
+case "${compiler}" in
     "gcc" )
         if [[ -f "/opt/rh/devtoolset-8/enable" ]]; then
             source /opt/rh/devtoolset-8/enable
@@ -97,12 +101,12 @@ case "${compiler:-gcc}" in
         _help 1
 esac
 
-if [[ "${cleanBefore:-no}" == "yes" ]]; then
+if [[ "${cleanBefore}" == "yes" ]]; then
     rm -rf "${buildDir}"
 fi
 
 mkdir -p "${buildDir}"
-if [[ "${keepLog:-no}" == "yes"  ]]; then
+if [[ "${keepLog}" == "yes"  ]]; then
     logName="${buildDir}/openroad-build-$(date +%s).log"
 else
     logName=/dev/null
diff --git a/etc/DockerHelper.sh b/etc/DockerHelper.sh
index 6fc60151130..53f390f76b4 100755
--- a/etc/DockerHelper.sh
+++ b/etc/DockerHelper.sh
@@ -102,7 +102,7 @@ _test() {
         echo "Could not find ${imagePath}, will attempt to create it" >&2
         _create
     fi
-    docker run --rm "${imagePath}" "./test/regression"
+    docker run --rm "${imagePath}" "./docker/test_wrapper.sh" "${compiler}" "./test/regression"
 }
 
 _create() {