Fix b-test issues

This commit fixes two issues:
  - run.sh fails if ccache is not available in the system. The fix
    is to ignore the return value of the which command.
  - there is a pip dependency conflict between yasha and Sphinx. The
    first depends on jinja<2.11 and the second on Jinja2>=2.3. The
    conflict is removed by upgrading yasha.
    This issue only affects setting-up the build environment.

Change-Id: Iab203cb299f0547c8683fc6d6394b23d25ea0b32
Signed-off-by: Gyorgy Szing <Gyorgy.Szing@arm.com>
diff --git a/tools/b-test/run.sh.j2 b/tools/b-test/run.sh.j2
index 557c0d8..6d0f33f 100644
--- a/tools/b-test/run.sh.j2
+++ b/tools/b-test/run.sh.j2
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Copyright (c) 2020-2022, Arm Limited and contributors. All rights reserved.
+# Copyright (c) 2020-2023, Arm Limited and contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -168,7 +168,7 @@
 	COLOR_GREEN=
 fi
 
-_ccache=$(which ccache)
+_ccache=$(which ccache 2>/dev/null) || true "never mind"
 
 case $1 in
 	{% for config in data %}