gn2bp: Add `-Wno-null-pointer-subtraction` to the default flags

Test: m cronet_aml_components_cronet_android_cronet
Change-Id: I129160617c30b977a39400a91d10ab8a5e61cb8f
diff --git a/tools/gn2bp/Android.bp.swp b/tools/gn2bp/Android.bp.swp
index 3255e5b..24e09cc 100644
--- a/tools/gn2bp/Android.bp.swp
+++ b/tools/gn2bp/Android.bp.swp
@@ -5103,6 +5103,7 @@
         "-Wno-macro-redefined",
         "-Wno-missing-field-initializers",
         "-Wno-non-virtual-dtor",
+        "-Wno-null-pointer-subtraction",
         "-Wno-sign-compare",
         "-Wno-sign-promo",
         "-Wno-unreachable-code-loop-increment",
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 747c45a..3d98ce6 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -1209,6 +1209,7 @@
       '-Wno-sign-compare',
       '-Wno-sign-promo',
       '-Wno-unused-parameter',
+      '-Wno-null-pointer-subtraction', # Needed to libevent
       '-Wno-deprecated-non-prototype', # needed for zlib
       '-fvisibility=hidden',
       '-Wno-ambiguous-reversed-operator', # needed for icui18n