Enable ninja-validations.sh

Update ninja to 1.11.1, which has validation actions,
and enable ninja-validations.sh
diff --git a/.github/workflows/cpp-ci.yml b/.github/workflows/cpp-ci.yml
index ca262a6..178d298 100644
--- a/.github/workflows/cpp-ci.yml
+++ b/.github/workflows/cpp-ci.yml
@@ -22,7 +22,7 @@
     - name: install ninja
       run: |
         mkdir -p ${GITHUB_WORKSPACE}/ninja-bin; cd ${GITHUB_WORKSPACE}/ninja-bin
-        wget https://github.com/ninja-build/ninja/releases/download/v1.10.2/ninja-linux.zip
+        wget https://github.com/ninja-build/ninja/releases/download/v1.11.1/ninja-linux.zip
         unzip ninja-linux.zip
         rm ninja-linux.zip
         echo "${GITHUB_WORKSPACE}/ninja-bin" >> "$GITHUB_PATH"
diff --git a/run_test.go b/run_test.go
index ffc3629..c8c12a5 100644
--- a/run_test.go
+++ b/run_test.go
@@ -240,10 +240,13 @@
 	}
 	args = append(args, "SHELL=/bin/bash")
 
+	var stderrb bytes.Buffer
 	cmd := exec.Command(args[0], args[1:]...)
 	cmd.Dir = dir
+	cmd.Stderr = &stderrb
 	output, _ := cmd.Output()
 	write("stdout", output)
+	write("stderr", stderrb.Bytes())
 	if isNinjaTest {
 		output = normalize(output, normalizeNinja)
 	}
diff --git a/testcase/ninja_validations.sh b/testcase/ninja_validations.sh
index cd77a01..33e9e7f 100644
--- a/testcase/ninja_validations.sh
+++ b/testcase/ninja_validations.sh
@@ -1,5 +1,4 @@
 #!/bin/bash
-# TODO(ninja): enable once upstream ninja supports validations
 #
 # Copyright 2015 Google Inc. All rights reserved
 #