include rule caching in PyInstaller build process (#2097)

* include rule caching in PyInstaller build process

The following commit introduces a new function that caches the capa
rule set, so that users don't have to manually run ./scripts/cache-
ruleset.py, before running pyinstaller.

* ci: omit Cache rule set step from build.yml workflow

* refactor: move cache generation to cache.py

* mkdir cache directory when it does not exist

---------

Co-authored-by: Soufiane Fariss <soufiane.fariss@um5s.net.ma>
Co-authored-by: Moritz <mr-tz@users.noreply.github.com>

.github/pyinstaller/pyinstaller.spec

@@ -1,10 +1,19 @@
 # -*- mode: python -*-
 # Copyright (C) 2020 Mandiant, Inc. All Rights Reserved.
-import os.path
-import subprocess
+import sys
 
 import wcwidth
+import capa.rules.cache
 
+from pathlib import Path
+
+# SPECPATH is a global variable which points to .spec file path
+capa_dir = Path(SPECPATH).parent.parent
+rules_dir = capa_dir / 'rules'
+cache_dir = capa_dir / 'cache'
+
+if not capa.rules.cache.generate_rule_cache(rules_dir, cache_dir):
+    sys.exit(-1)
 
 a = Analysis(
     # when invoking pyinstaller from the project root,
@@ -26,7 +35,7 @@ a = Analysis(
         # so we manually embed the wcwidth resources here.
         #
         # ref: https://stackoverflow.com/a/62278462/87207
-        (os.path.dirname(wcwidth.__file__), "wcwidth"),
+        (Path(wcwidth.__file__).parent, "wcwidth"),
     ],
     # when invoking pyinstaller from the project root,
     # this gets run from the project root.

.github/workflows/build.yml

@@ -52,8 +52,6 @@ jobs:
         run: python -m pip install --upgrade pip setuptools
       - name: Install capa with build requirements
         run: pip install -e .[build]
-      - name: Cache the rule set
-        run: python ./scripts/cache-ruleset.py ./rules/ ./cache/
       - name: Build standalone executable
         run: pyinstaller --log-level DEBUG .github/pyinstaller/pyinstaller.spec
       - name: Does it run (PE)?