scripts: Convert the build-efi script to avoid sudo

Make use of the mk_fs() function to avoid needing to use sudo to mount
the loopback partition. This makes the script a little more friendly for
those nervous about sudo in their tools.

Signed-off-by: Simon Glass <sjg@chromium.org>

scripts/build_helper.py

@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+"""Common script for build- scripts
+
+"""
+
+import contextlib
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+OUR_PATH = os.path.dirname(os.path.realpath(__file__))
+OUR1_PATH = os.path.dirname(OUR_PATH)
+
+# Bring in the patman and test libraries (but don't override the first path in
+# PYTHONPATH)
+sys.path.insert(2, os.path.join(OUR1_PATH, 'tools'))
+sys.path.insert(2, os.path.join(OUR1_PATH, 'test/py/tests'))
+
+from u_boot_pylib import command
+from u_boot_pylib import tools
+import fs_helper
+
+
+class Helper:
+    def __init__(self):
+        self.settings = None
+
+    @contextlib.contextmanager
+    def make_disk(self, fname, size_mb=20, fs_type='ext4', use_part=False):
+        """Create a raw disk image with files on it
+
+        Args:
+            fname (str): Filename to write the images to
+            fs_type (str): Filesystem type to create (ext4 or vfat)
+            size_mb (int): Size in MiB
+            use_part (bool): True to create a partition table, False to use a
+                raw disk image
+
+        Yields:
+            str: Directory to write the files into
+        """
+        with tempfile.NamedTemporaryFile() as tmp:
+            with tempfile.TemporaryDirectory(prefix='build_helper.') as dirname:
+                try:
+                    yield dirname
+                    fs_helper.mk_fs(None, fs_type, size_mb << 20, None, dirname,
+                                    fs_img=tmp.name, quiet=True)
+                finally:
+                    pass
+
+            if use_part:
+                with open(fname, 'wb') as img:
+                    img.truncate(size_mb << 20)
+                    img.seek(1 << 20, 0)
+                    img.write(tools.read_file(tmp.name))
+                subprocess.run(
+                    ['sfdisk', fname], text=True, check=True,
+                    capture_output=True,
+                    input=f'type=c, size={size_mb-1}M, start=1M,bootable')
+            else:
+                shutil.copy2(tmp.name, fname)