fix test_cmake_as_package fail

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>

scripts/mbedtls_dev/build_tree.py

@@ -17,12 +17,15 @@
 # limitations under the License.
 
 import os
+import inspect
+
 
 def looks_like_mbedtls_root(path: str) -> bool:
     """Whether the given directory looks like the root of the Mbed TLS source tree."""
     return all(os.path.isdir(os.path.join(path, subdir))
                for subdir in ['include', 'library', 'programs', 'tests'])
 
+
 def chdir_to_root() -> None:
     """Detect the root of the Mbed TLS source tree and change to it.
 
@@ -36,3 +39,21 @@ def chdir_to_root() -> None:
             os.chdir(d)
             return
     raise Exception('Mbed TLS source tree not found')
+
+
+def guess_mbedtls_root():
+    """Guess mbedTLS source code directory.
+
+    Return the first possible mbedTLS root directory
+    """
+    dirs = set({})
+    for i in inspect.stack():
+        path = os.path.dirname(i.filename)
+        for d in ['.', os.path.pardir, os.path.join(*([os.path.pardir]*2))]:
+            d = os.path.abspath(os.path.join(path, d))
+            if d in dirs:
+                continue
+            dirs.add(d)
+            if looks_like_mbedtls_root(d):
+                return d
+    raise Exception('Mbed TLS source tree not found')