Default complete the build with failing timing

The build script will look in the logs to determine failure later

Change-Id: Ieee80952ee3e5d9eb5fbb924edd5b0e688e234b3

hw/top_matcha/util/vivado_hook_write_bitstream_pre.tcl

diff --git a/hw/top_matcha/util/vivado_hook_write_bitstream_pre.tcl b/hw/top_matcha/util/vivado_hook_write_bitstream_pre.tcl
index 054d3ec..6938617 100644
--- a/hw/top_matcha/util/vivado_hook_write_bitstream_pre.tcl
+++ b/hw/top_matcha/util/vivado_hook_write_bitstream_pre.tcl
@@ -19,10 +19,14 @@
 set slack_ns [get_property SLACK [get_timing_paths -delay_type min_max]]
 send_msg "Designcheck 1-2" INFO "Slack is ${slack_ns} ns."
 
-if [expr {$slack_ns < 0}] {
-  send_msg "Designcheck 1-3" ERROR "Timing failed. Slack is ${slack_ns} ns."
+if {
+    [info exists ::env(VIVADO_FAIL_ON_TIMING)]
+    && $::env(VIVADO_FAIL_ON_TIMING) != 0
+} then {
+    if [expr {$slack_ns < 0}] {
+        send_msg "Designcheck 1-3" ERROR "Timing failed. Slack is ${slack_ns} ns."
+    }
 }
-
 # Enable bitstream identification via USR_ACCESS register.
 set_property BITSTREAM.CONFIG.USR_ACCESS TIMESTAMP [current_design]