tests: llext-edk: get the Zephyr SDK path from build_info.yml

The LLEXT EDK test works by packaging an EDK and then testing its
functionality to build the extension in an external CMake build step.
That CMakelists.txt file currently references the required tools using
the ZEPHYR_SDK_INSTALL_DIR environment variable, which must be manually
set by the user.

This change modifies the test to read the newly added 'build_info.yml'
file, generated by Zephyr during the first build step. This allows to
set the ZEPHYR_SDK_INSTALL_DIR environment variable automatically based
on the (possibly auto-discovered) SDK path.

A few minor compliance cleanups are also included.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

tests/misc/llext-edk/pytest/test_edk.py

@@ -10,16 +10,22 @@
 from subprocess import check_output
 
 import pytest
+import yaml
 from twister_harness import DeviceAdapter
 
 logger = logging.getLogger(__name__)
 
+
 def test_edk(unlaunched_dut: DeviceAdapter):
-    # Need to have the ZEPHYR_SDK_INSTALL_DIR environment variable set,
-    # otherwise can't actually build the edk
-    if os.environ.get("ZEPHYR_SDK_INSTALL_DIR") is None:
-        logger.warning("ZEPHYR_SDK_INSTALL_DIR is not set, skipping test")
-        pytest.skip("ZEPHYR_SDK_INSTALL_DIR is not set")
+    # Get the SDK path from build_info.yml
+    build_dir = str(unlaunched_dut.device_config.build_dir)
+    with open(Path(build_dir) / "build_info.yml") as f:
+        build_info = yaml.safe_load(f)
+        if build_info["cmake"]["toolchain"]["name"] != "zephyr":
+            logger.warning("This test requires the Zephyr SDK to be used, skipping")
+            pytest.skip("The Zephyr SDK must be used")
+
+        sdk_dir = build_info["cmake"]["toolchain"]["path"]
 
     # Can we build the edk?
     command = [
@@ -64,6 +70,7 @@ def test_edk(unlaunched_dut: DeviceAdapter):
             # knows where the EDK is installed
             edk_dir = Path(tempdir) / "llext-edk"
             env = os.environ.copy()
+            env.update({"ZEPHYR_SDK_INSTALL_DIR": sdk_dir})
             env.update({"LLEXT_EDK_INSTALL_DIR": edk_dir})
 
             # Build the extension using the edk
@@ -92,7 +99,7 @@ def test_edk(unlaunched_dut: DeviceAdapter):
                 "--build-dir",
                 unlaunched_dut.device_config.build_dir,
                 "--",
-                f"-DEXTENSION_DIR={tempdir_extension}/build/"
+                f"-DEXTENSION_DIR={tempdir_extension}/build/",
             ]
             logger.debug(f"west command: {command}")
             output = check_output(command, text=True)