Fix concurrent DAML compilations on Windows

Since Windows builds aren’t sandboxed properly (see
bazelbuild/bazel#5136), concurrent
compilations interact with the same tmp_db directory which leads to
flaky build failures.

daml-foundations/daml-ghc/package-database/util.bzl

@@ -77,14 +77,14 @@ def _daml_package_rule_impl(ctx):
         progress_message = "Compiling " + name + ".daml to daml-lf " + ctx.attr.daml_lf_version,
         command = """
       set -eou pipefail
-      mkdir -p tmp_db
-      tar xf {db_tar} -C tmp_db --strip-components 1
-      mkdir -p tmp_db/{daml_lf_version}
+      PACKAGEDB=$(mktemp -d)
+      tar xf {db_tar} -C "$PACKAGEDB" --strip-components 1
+      mkdir -p "$PACKAGEDB"/{daml_lf_version}
 
       # Compile the dalf file
       {damlc_bootstrap} compile \
         --package-name {pkg_name} \
-        --package-db tmp_db \
+        --package-db "$PACKAGEDB" \
         --write-iface \
         --target {daml_lf_version} \
         -o {dalf_file} \