gn2bp: Normalize args by for loop instead of comprehension

Upcoming CL will make this normalization a bit more complex, this CL is
a preparation for that.

Test: ./update_results.
Change-Id: I8248c68d30b21682f5521435f85cd555033b51c6
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 5a49d4f..5295fde 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -620,8 +620,14 @@
   def __init__(self, target):
     # Just to be on the safe side, create a deep-copy.
     self.target = copy.deepcopy(target)
+    self.target.args = self._normalize_args()
+
+  def _normalize_args(self):
     # Convert ['--param=value'] to ['--param', 'value'] for consistency.
-    self.target.args = [str for it in self.target.args for str in it.split('=')]
+    normalized_args = []
+    for arg in self.target.args:
+      normalized_args.extend(arg.split('='))
+    return normalized_args
 
   # There are three types of args:
   # - flags (--flag)