Add a possibility to set PLATFORM_ARCH_TYPE with an environment variable

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
Change-Id: I364335d4cec9d258354bd3f52e75f452886dc4db
diff --git a/lib/boot_data.py b/lib/boot_data.py
index 9755cef..7b918fa 100755
--- a/lib/boot_data.py
+++ b/lib/boot_data.py
@@ -29,7 +29,8 @@
 redfish_support_trans_state = int(os.environ.get('REDFISH_SUPPORT_TRANS_STATE', 0)) or \
     int(BuiltIn().get_variable_value("${REDFISH_SUPPORT_TRANS_STATE}", default=0))
 
-platform_arch_type = BuiltIn().get_variable_value("${PLATFORM_ARCH_TYPE}", default="power")
+platform_arch_type = os.environ.get('PLATFORM_ARCH_TYPE', '') or \
+    BuiltIn().get_variable_value("${PLATFORM_ARCH_TYPE}", default="power")
 
 
 def create_boot_table(file_path=None,