Kokoro: Move the clean checkout to tmpfs

tmpfs is where the real disk space lives.
Fixes spurious out-of-disk errors.

Change-Id: Icd82b58888f5ffa26680c9f68cd65e7b53874bf5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/64541
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

kokoro/linux/build.sh

@@ -19,10 +19,24 @@ set -e # Fail on any error.
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd )"
 ROOT_DIR="$( cd "${SCRIPT_DIR}/../.." >/dev/null 2>&1 && pwd )"
 
+# Inside the docker VM, we clone the project to a new directory.
+# We do this so that the docker script can be tested in a local development
+# checkout, without having the build litter the local checkout with artifacts.
+# This directory is mapped to the host temporary directory.
+# Kokoro uses a '/tmpfs' root, where as most linux enviroments just have '/tmp'
+if [ -d "/tmpfs" ]; then
+    TMP_DIR=/tmpfs
+else
+    TMP_DIR=/tmp
+fi
+
+
 docker run --rm -i \
   --volume "${ROOT_DIR}:${ROOT_DIR}" \
+  --volume "${TMP_DIR}:/src" \
   --volume "${KOKORO_ARTIFACTS_DIR}:/mnt/artifacts" \
   --workdir "${ROOT_DIR}" \
+  --env SRC_DIR="/src/tint" \
   --env BUILD_TYPE=$BUILD_TYPE \
   --env BUILD_SYSTEM=$BUILD_SYSTEM \
   --env BUILD_SANITIZER=$BUILD_SANITIZER \

kokoro/linux/docker.sh

@@ -54,7 +54,7 @@ function with_retry {
   done
 }
 
-ORIGINAL_SRC_DIR="$(pwd)"
+CLONE_SRC_DIR="$(pwd)"
 
 . /bin/using.sh # Declare the bash `using` function for configuring toolchains.
 
@@ -62,13 +62,11 @@ using depot_tools
 using go-1.14.4      # Speeds up ./tools/lint
 using doxygen-1.8.18
 
-status "Cloning to clean source directory"
-# We do this so that the docker script can be tested in a local development
-# checkout, without having the build litter the local checkout with artifacts
-SRC_DIR=/tmp/tint-src
+status "Cloning to clean source directory at '${SRC_DIR}'"
+
 mkdir -p ${SRC_DIR}
 cd ${SRC_DIR}
-git clone ${ORIGINAL_SRC_DIR} .
+git clone ${CLONE_SRC_DIR} .
 
 status "Fetching dependencies"
 cp standalone.gclient .gclient