build_packages: Remove unused argument (eventfile)

BUG=b:216196955
TEST=Did not find usages in cs/, CQ

Change-Id: Ic12459653bf8931da3d68ea829729a898301741d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/3414035
Tested-by: Cindy Lin <xcl@google.com>
Auto-Submit: Cindy Lin <xcl@google.com>
Reviewed-by: Ram Chandrasekar <rchandrasekar@google.com>
Commit-Queue: Ram Chandrasekar <rchandrasekar@google.com>
diff --git a/build_packages b/build_packages
index 1d5cd21..66286e5 100755
--- a/build_packages
+++ b/build_packages
@@ -26,8 +26,6 @@
   "Build autotest client code."
 DEFINE_boolean withdebugsymbols "${FLAGS_FALSE}" \
   "Install the debug symbols for all packages"
-DEFINE_string eventfile "${DEFAULT_EVENT_FILE}" \
-  "Define the file that event logs will be written."
 DEFINE_boolean withrevdeps "${FLAGS_TRUE}" \
   "Calculate reverse dependencies on changed ebuilds."
 DEFINE_boolean autosetgov "${FLAGS_FALSE}" \