jansson: add run_tests.sh (#13596)

`infra/experimental/chronos/check_tests.sh jansson c`

```
...
PASS: run-suites
============================================================================
Testsuite summary for jansson 2.14.1
============================================================================
# TOTAL: 1
# PASS:  1
# SKIP:  0
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================
make[4]: Leaving directory '/src/jansson/test'
make[3]: Leaving directory '/src/jansson/test'
make[2]: Leaving directory '/src/jansson/test'
make[1]: Leaving directory '/src/jansson/test'
make[1]: Entering directory '/src/jansson'
make  check-TESTS
make[2]: Entering directory '/src/jansson'
make[3]: Entering directory '/src/jansson'
SKIP: scripts/clang-format-check
============================================================================
Testsuite summary for jansson 2.14.1
============================================================================
# TOTAL: 1
# PASS:  0
# SKIP:  1
# XFAIL: 0
# FAIL:  0
# XPASS: 0
# ERROR: 0
============================================================================
make[3]: Leaving directory '/src/jansson'
make[2]: Leaving directory '/src/jansson'
make[1]: Leaving directory '/src/jansson'
```

Signed-off-by: Adam Korczynski <adam@adalogics.com>

Author: AdamKorcz

projects/jansson/Dockerfile

@@ -19,4 +19,4 @@ FROM gcr.io/oss-fuzz-base/base-builder
 RUN git clone --depth 1 https://github.com/akheron/jansson.git /src/jansson
 
 WORKDIR $SRC/jansson
-COPY build.sh $SRC/
+COPY build.sh run_tests.sh $SRC/

projects/jansson/run_tests.sh

@@ -0,0 +1,18 @@
+#!/bin/bash -eu
+# Copyright 2025 Google LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+
+make check