yocto-kernel: enforce exact match for BBLAYERS

The current code uses .startswith to find BBLAYERS, which causes false
positives when other variables such as BBLAYERS_NON_REMOVABLE exist.

This forces an exact match instead of a partial match.

Fixes [YOCTO #4743].

(From meta-yocto master rev: c039def50ca6c02cb1b66fd4bf76664de42c068e)

(From meta-yocto rev: bb46a14833d18000e87b76d06df04ef9a7f40afb)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/bsp/kernel.py

@@ -54,7 +54,8 @@ def find_bblayers(scripts_path):
     in_bblayers = False
     for line in lines:
         line = line.strip()
-        if line.strip().startswith("BBLAYERS"):
+        tokens = line.split()
+        if len(tokens) > 0 and tokens[0] == 'BBLAYERS':
             bblayers_lines.append(line)
             in_bblayers = True
             quotes = line.strip().count('"')