Fix doxygen run in jenkins

Summary:
The buildables stash rule only stashes files beginning with `bazel_`.
As a result `run_doxygen` never exists in the docs runtime stage even though
the build deps stage might create it.
We are also checking for empty cc targets instead of non empty to determine
whether we should run doxygen.
Note that this has been broken since D6922 :(

This fixes both problems.

Test Plan: This diff should cause doxygen to run.

Reviewers: zasgar, oazizi, michelle

Reviewed By: oazizi

Signed-off-by: Vihang Mehta <vihang@pixielabs.ai>

Differential Revision: https://phab.corp.pixielabs.ai/D12635

GitOrigin-RevId: e0af41751a5cb426e2990675fff1846997be95d3

Jenkinsfile

@@ -918,10 +918,10 @@ builders['Lint & Docs'] = {
       sh 'arc lint --trace'
     }
 
-    if (shFileExists('run_doxygen')) {
+    if (shFileExists('bazel_run_doxygen')) {
       def stashName = 'doxygen-docs'
       container('pxbuild') {
-        sh 'doxygen'
+        sh 'LD_LIBRARY_PATH="" doxygen'
       }
       container('gcloud') {
         stashOnGCS(stashName, 'docs/html')

ci/bazel_build_deps.sh

@@ -97,7 +97,7 @@ done
 
 targets=()
 function compute_targets() {
-  if [ "${all_targets}" = "true" ]; then
+  if [[ "${all_targets}" = "true" ]]; then
     targets=("//...")
     return 0
   fi
@@ -176,7 +176,7 @@ ${bazel_query} "${cc_tests} ${bpf_excludes}" > bazel_tests_gcc_opt 2>/dev/null
 ${bazel_query} "${cc_buildables} ${bpf_excludes} ${sanitizer_only}" > bazel_buildables_sanitizer 2>/dev/null
 ${bazel_query} "${cc_tests} ${bpf_excludes} ${sanitizer_only}" > bazel_tests_sanitizer 2>/dev/null
 
-if [ "${run_bpf_targets}" = "true" ]; then
+if [[ "${run_bpf_targets}" = "true" ]]; then
   # BPF.
   ${bazel_query} "${bpf_buildables}" > bazel_buildables_bpf 2>/dev/null
   ${bazel_query} "${bpf_tests}" > bazel_tests_bpf 2>/dev/null
@@ -204,6 +204,6 @@ ${bazel_query} "${go_tests} ${go_xcompile_excludes}" > bazel_tests_go_race 2>/de
 
 # Should we run doxygen?
 bazel_cc_touched=$(${bazel_query} "${cc_buildables} union ${cc_tests}" 2>/dev/null)
-if [ "${all_targets}" = "true" ] || [[ -z $bazel_cc_touched ]]; then
-  touch run_doxygen
+if [[ "${all_targets}" = "true" || -n $bazel_cc_touched ]]; then
+  touch bazel_run_doxygen
 fi