build: Add logic to use default extensions if none are found

Currently, the Bazel build may fail if symlinks to the Bazel
extension files are not linked to the proper locations.

To make sure the build always works (falling back on default
extensions), configure the script to create the symlinks to the
default files in case they don't exist or are broken symlinks.

Change-Id: Ie385e4ede912d0f40026ef6c78a9c2fb60ca8924
Signed-off-by: John Moon <quic_johmoo@quicinc.com>

build_with_bazel.py

@@ -3,6 +3,7 @@
 # Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
 
 import argparse
+import errno
 import logging
 import os
 import re
@@ -13,6 +14,10 @@ CPU = "aarch64"
 HOST_CROSSTOOL = "@bazel_tools//tools/cpp:toolchain"
 HOST_TARGETS = ["dtc"]
 DEFAULT_SKIP_LIST = ["abi", "test_mapping"]
+MSM_EXTENSIONS = "build/msm_kernel_extensions.bzl"
+ABL_EXTENSIONS = "build/abl_extensions.bzl"
+DEFAULT_MSM_EXTENSIONS_SRC = "../msm-kernel/msm_kernel_extensions.bzl"
+DEFAULT_ABL_EXTENSIONS_SRC = "../bootable/bootloader/edk2/abl_extensions.bzl"
 
 
 class BazelBuilder:
@@ -33,6 +38,7 @@ class BazelBuilder:
         self.skip_list = skip_list
         self.user_opts = user_opts
         self.process_list = []
+        self.setup_extensions()
 
     def __del__(self):
         for proc in self.process_list:
@@ -48,6 +54,29 @@ class BazelBuilder:
             "--host_crosstool_top={}".format(HOST_CROSSTOOL),
         ]
 
+    def setup_extensions(self):
+        """Set up the extension files if needed"""
+        for (ext, def_src) in [
+            (MSM_EXTENSIONS, DEFAULT_MSM_EXTENSIONS_SRC),
+            (ABL_EXTENSIONS, DEFAULT_ABL_EXTENSIONS_SRC),
+        ]:
+            ext_path = os.path.join(self.workspace, ext)
+            # If the file doesn't exist or is a dead link, link to the default
+            try:
+                os.stat(ext_path)
+            except OSError as e:
+                if e.errno == errno.ENOENT:
+                    logging.info(
+                        "%s does not exist or is a broken symlink... linking to default at %s",
+                        ext,
+                        def_src,
+                    )
+                    if os.path.islink(ext_path):
+                        os.unlink(ext_path)
+                    os.symlink(def_src, ext_path)
+                else:
+                    raise e
+
     def get_build_targets(self):
         """Query for build targets"""
         logging.info("Querying build targets...")