diff --git a/bypy/linux/__main__.py b/bypy/linux/__main__.py
index acff193a92..3768195bda 100644
--- a/bypy/linux/__main__.py
+++ b/bypy/linux/__main__.py
@@ -276,9 +276,9 @@ def create_tarfile(env, compression_level='9'):
     try:
         shutil.rmtree(base)
     except EnvironmentError as err:
-        if err.errno != errno.ENOENT:
+        if err.errno not in (errno.ENOENT, errno.EBUSY):
             raise
-    os.mkdir(base)
+    os.makedirs(base, exist_ok=True)  # when base is a mount point deleting it fails with EBUSY
     dist = os.path.join(base, '%s-%s-%s.tar' % (calibre_constants['appname'], calibre_constants['version'], arch))
     with tarfile.open(dist, mode='w', format=tarfile.PAX_FORMAT) as tf:
         cwd = os.getcwd()
diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index 53c8de0ed2..898caad665 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -316,6 +316,9 @@ class BuildTest(unittest.TestCase):
             raise unittest.SkipTest('Skipping Qt build test as sanitizer is enabled')
         from qt.core import QApplication, QFontDatabase, QImageReader, QLoggingCategory, QNetworkAccessManager, QSslSocket, QTimer
         QLoggingCategory.setFilterRules('''qt.webenginecontext.debug=true''')
+        if hasattr(os, 'geteuid') and os.geteuid() == 0:
+            # likely a container build, webengine cannot run as root with sandbox
+            os.environ['QTWEBENGINE_CHROMIUM_FLAGS'] = '--no-sandbox'
         from qt.webengine import QWebEnginePage
 
         from calibre.utils.img import image_from_data, image_to_data, test