device.mk: Freeze vendor security patch 2021-09-05

(stopship hack) Freeze the SPL so that we can test more
rollback cases in testing before launch.

Bug: 187105270
Change-Id: Icb475d6c3331d26a6b5314cbb0cdf2cbe1428a27
diff --git a/device.mk b/device.mk
index ef2e115..3a27ccb 100644
--- a/device.mk
+++ b/device.mk
@@ -26,8 +26,13 @@
 	FILESYSTEM_TYPE_system=ext4 \
 POSTINSTALL_OPTIONAL_system=true
 
+ifneq (,$(filter userdebug eng, $(TARGET_BUILD_VARIANT)))
+# STOPSHIP (b/187105270) hack: temp freeze to a lower security patch
+VENDOR_SECURITY_PATCH = 2021-09-05
+else
 # Set Vendor SPL to match platform
 VENDOR_SECURITY_PATCH = $(PLATFORM_SECURITY_PATCH)
+endif
 
 # Set boot SPL
 BOOT_SECURITY_PATCH = $(PLATFORM_SECURITY_PATCH)