[dv, bazel] : run opentitantool with shared libs outside system lib path

This commit enables opentitantool to find and link to its
library dependencies like libftdi, libusb, libudev that are installed in
 user's work area. This is particularly useful when the user's compute
enironment does not have these libraries preinstalled as part of the
system and the user doesn't have root permissions to install these
libraries using syatem package managers. While the custom paths to the
headers and shared libs needed for building the opentitantool can be
specified by setting the PKG_CONFIG_PATH environment variable through the
bazel build action_env property in site specific .bazelrc-site file,
these paths are not available in the bazel sandbox that runs the
opentitantool to generate the otp json.
for example, bazel build //hw/ip/otp_ctrl/data:otp_json_alert_digest_cfg.
Attempts to pass in the user provided LD_LIBRARY_PATH using the bazel
build action_env fail as this doesn't get propagated to the bazel
subcommand that runs the opentitantool. Hence adding
use_default_shell_env = True which then allows the LD_LIBRARY_PATH
specified via the action_env to be made available to the opentitantool
run sandbox.

Signed-off-by: Venkat Krishnan <[email protected]>

rules/otp.bzl

@@ -198,11 +198,20 @@ def _otp_alert_digest_impl(ctx):
     args.add_all(("--rcfile=", "otp", "alert-digest", ctx.file.otp_img))
     args.add("--output", file)
 
+    # By default, no environment variables are available to the action
+    # during bazel builds. This can not be changed with action_env.
+    # However, the opentitantool binary used in building the json target
+    # needs access to LD_LIBRARY_PATH to load shared libraries
+    # outside standard system paths.
+    # Setting use_default_shell_env to True allows passing LD_LIBRARY_PATH
+    # to the sandbox using --action_env switch
+
     ctx.actions.run(
         outputs = outputs,
         inputs = inputs,
         arguments = [args],
         executable = tc.tools.opentitantool,
+        use_default_shell_env = True,
     )
     return [DefaultInfo(files = depset([file]))]