use mktemp to avoid hardcoding temp dir.

tools/internal_ci/linux/grpc_bazel_on_foundry_opt.sh

@@ -21,11 +21,11 @@ set -ex
 mkdir -p ${KOKORO_KEYSTORE_DIR}
 cp ${KOKORO_GFILE_DIR}/GrpcTesting-d0eeee2db331.json ${KOKORO_KEYSTORE_DIR}/4321_grpc-testing-service
 
-mkdir -p /tmpfs/tmp/bazel-canary
-ln -f "${KOKORO_GFILE_DIR}/bazel-canary" /tmpfs/tmp/bazel-canary/bazel
+temp_dir=`mktemp -d`
+ln -f "${KOKORO_GFILE_DIR}/bazel-canary" ${temp_dir}/bazel
 chmod 755 "${KOKORO_GFILE_DIR}/bazel-canary"
-export PATH="/tmpfs/tmp/bazel-canary:${PATH}"
-# This should show /tmpfs/tmp/bazel-canary/bazel
+export PATH="${temp_dir}:${PATH}"
+# This should show ${temp_dir}/bazel
 which bazel
 chmod +x "${KOKORO_GFILE_DIR}/bazel_wrapper.py"
 
@@ -50,7 +50,7 @@ source tools/internal_ci/helper_scripts/prepare_build_linux_rc
   --strategy=Closure=remote  \
   --genrule_strategy=remote  \
   --experimental_strict_action_env=true \
-  --experimental_remote_platform_override='properties:{name:"container-image" value:"docker://gcr.io/asci-toolchain/nosla-debian8-clang-fl@sha256:b2d946c1ddc20af250fe85cf98bd648ac5519131659f7c36e64184b433175a33" }' \
+  --experimental_remote_platform_override='properties:{name:"container-image" value:"docker://gcr.io/cloud-marketplace/google/rbe-debian8@sha256:b2d946c1ddc20af250fe85cf98bd648ac5519131659f7c36e64184b433175a33" }' \
   --crosstool_top=@com_github_bazelbuild_bazeltoolchains//configs/debian8_clang/0.3.0/bazel_0.10.0:toolchain \
   --define GRPC_PORT_ISOLATED_RUNTIME=1 \
   -c opt \

tools/internal_ci/linux/grpc_tsan_on_foundry.sh

@@ -22,11 +22,11 @@ set -ex
 mkdir -p ${KOKORO_KEYSTORE_DIR}
 cp ${KOKORO_GFILE_DIR}/GrpcTesting-d0eeee2db331.json ${KOKORO_KEYSTORE_DIR}/4321_grpc-testing-service
 
-mkdir -p /tmpfs/tmp/bazel-canary
-ln -f "${KOKORO_GFILE_DIR}/bazel-canary" /tmpfs/tmp/bazel-canary/bazel
+temp_dir = mktemp -d
+ln -f "${KOKORO_GFILE_DIR}/bazel-canary" ${temp_dir}/bazel
 chmod 755 "${KOKORO_GFILE_DIR}/bazel-canary"
-export PATH="/tmpfs/tmp/bazel-canary:${PATH}"
-# This should show /tmpfs/tmp/bazel-canary/bazel
+export PATH="${temp_dir}:${PATH}"
+# This should show ${temp_dir}/bazel
 which bazel
 chmod +x "${KOKORO_GFILE_DIR}/bazel_wrapper.py"