Fix incorrect suppression of compiler errors in cirque tests. (#3317)

ninja sends all output, including compiler errors, to stdout, not
stderr.  So redirecting to /dev/null was hiding compiler errors and
making it very difficult to debug test failures.

src/test_driver/linux-cirque/OnOffClusterTest.sh

@@ -31,7 +31,7 @@ function build_chip_tool() {
     set -x
     cd "$chip_tool_dir"
     gn gen out/debug >/dev/null
-    ninja -C out/debug >/dev/null
+    run_ninja -C out/debug
     docker build -t chip_tool -f Dockerfile . >/dev/null 2>&1
 }
 
@@ -40,7 +40,7 @@ function build_chip_lighting() {
     set -x
     cd "$chip_light_dir"
     gn gen out/debug --args='bypass_rendezvous=true' >/dev/null
-    ninja -C out/debug >/dev/null
+    run_ninja -C out/debug
     docker build -t chip_server -f Dockerfile . >/dev/null 2>&1
     set +x
 }
@@ -53,4 +53,5 @@ function main() {
     python3 "$SOURCE_DIR/test-on-off-cluster.py"
 }
 
+source "$SOURCE_DIR"/shell-helpers.sh
 main

src/test_driver/linux-cirque/shell-helpers.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# This function is a workaround for the fact that ninja sends all
+# output, including compiler errors, to stdout, not stderr.  We want
+# to suppress the various output from ninja itself, but not compiler
+# errors.  Do that by prefixing the ninja output with a string that is
+# unlikely to appear in compiler errors, then filtering it out.
+function run_ninja() {
+    prefix="|ninja_filter_prefix|"
+    NINJA_STATUS="$prefix[%f/%t] " ninja "$@" | grep -v "^$prefix"
+}