Clean before running daml build (#2816)

This should hopefully fix some of the flakiness we’ve been seeing on
Windows. Not entirely sure what’s going wrong without the clean but
since this only happens the lack of sandboxing seems like the most
likely difference.

triggers/daml/BUILD.bazel

@@ -9,17 +9,21 @@ genrule(
     srcs = glob(["**/*.daml"]),
     outs = ["trigger.dar"],
     cmd = """
-      cat << EOF > daml.yaml
+      set -eou pipefail
+      TMP_DIR=$$(mktemp -d)
+      mkdir -p $$TMP_DIR/daml/Daml
+      cp -L $(location Daml/Trigger.daml) $$TMP_DIR/daml/Daml
+      cat << EOF > $$TMP_DIR/daml.yaml
 sdk-version: 0.0.0
 name: trigger
-source: triggers/daml
+source: daml
 version: 0.0.1
 dependencies:
   - daml-stdlib
   - daml-prim
 EOF
-
-      $(location //compiler/damlc) build -o $(location trigger.dar)
+      $(location //compiler/damlc) build --project-root=$$TMP_DIR -o $$PWD/$(location trigger.dar)
+      rm -rf $$TMP_DIR
     """,
     tools = ["//compiler/damlc"],
     visibility = ["//visibility:public"],

triggers/tests/BUILD.bazel

@@ -19,18 +19,22 @@ genrule(
     outs = ["acs.dar"],
     cmd = """
       set -eou pipefail
-      cat << EOF > daml.yaml
+      TMP_DIR=$$(mktemp -d)
+      mkdir -p $$TMP_DIR/daml
+      cp -L $(location :daml/ACS.daml) $$TMP_DIR/daml
+      cp -L $(location //triggers/daml:trigger.dar) $$TMP_DIR/
+      cat << EOF > $$TMP_DIR/daml.yaml
 sdk-version: 0.0.0
 name: acs
-source: triggers/tests/daml
+source: daml
 version: 0.0.1
 dependencies:
   - daml-stdlib
   - daml-prim
-  - $(location //triggers/daml:trigger.dar)
+  - trigger.dar
 EOF
-
-      $(location //compiler/damlc) build -o $(location acs.dar)
+      $(location //compiler/damlc) build --project-root=$$TMP_DIR -o $$PWD/$(location acs.dar)
+      rm -rf $$TMP_DIR
     """,
     tools = ["//compiler/damlc"],
     visibility = ["//visibility:public"],