enable unit tests to run on Windows

Signed-off-by: Will Murphy <will.murphy@anchore.com>

Taskfile.yaml

@@ -9,6 +9,7 @@ vars:
   SNAPSHOT_DIR: snapshot
   CHANGELOG: CHANGELOG.md
   NEXT_VERSION: VERSION
+  MAKEDIR_P: 'python -c "import sys; import os; os.makedirs(sys.argv[1], exist_ok=True)"'
 
 tasks:
 
@@ -127,7 +128,7 @@ tasks:
       # unit test coverage threshold (in % coverage)
       COVERAGE_THRESHOLD: 45
     cmds:
-      - cmd: "mkdir -p {{ .TMP_DIR }}"
+      - cmd: "{{ .MAKEDIR_P }} {{ .TMP_DIR }}"
         silent: true
       - "go test -coverprofile {{ .TMP_DIR }}/unit-coverage-details.txt {{ .TEST_PKGS }}"
       - cmd: ".github/scripts/coverage.py {{ .COVERAGE_THRESHOLD }} {{ .TMP_DIR }}/unit-coverage-details.txt"