CI tests: re-enable clang thread sanitizer test (#5826)

This PR re-enables the thread sanitizer CI test.
The issues that we experienced
(#5492) were ultimately caused
by the fact that thread sanitizer is not able to automatically load
`libarcher` under some Linux distributions like Ubuntu, and `libarcher`
is required to avoid false positives with OpenMP ! The fix is adding
this line ( see https://hpc-wiki.info/hpc/ThreadSanitizer ):
```
export OMP_TOOL_LIBRARIES=/usr/lib/llvm-17/lib/libarcher.so
``` 
In addition to this change, the PR adds some comments. Moreover, WarpX
is now compiled always with EB support, since this is now the default
and since this (slightly) reduces the time required to run this CI test.

Author: lucafedeli88

.github/workflows/clang_sanitizers.yml

@@ -79,8 +79,7 @@ jobs:
   build_thread_sanitizer:
     name: Clang thread sanitizer
     runs-on: ubuntu-24.04
-    # TODO Fix data race conditions and re-enable job
-    if: 0 #github.event.pull_request.draft == false
+    if: github.event.pull_request.draft == false
     env:
       CC: clang
       CXX: clang++
@@ -118,34 +117,33 @@ jobs:
           -DWarpX_QED=ON                    \
           -DWarpX_QED_TABLE_GEN=ON          \
           -DWarpX_OPENPMD=ON                \
-          -DWarpX_EB=OFF                    \
           -DWarpX_PRECISION=DOUBLE          \
           -DWarpX_PARTICLE_PRECISION=DOUBLE
         cmake --build build -j 4
 
-        cmake -S . -B build_EB              \
-          -GNinja                           \
-          -DCMAKE_VERBOSE_MAKEFILE=ON       \
-          -DCMAKE_BUILD_TYPE=RelWithDebInfo \
-          -DWarpX_DIMS="2"                  \
-          -DWarpX_FFT=ON                    \
-          -DWarpX_QED=ON                    \
-          -DWarpX_QED_TABLE_GEN=ON          \
-          -DWarpX_OPENPMD=ON                \
-          -DWarpX_EB=ON                     \
-          -DWarpX_PRECISION=DOUBLE          \
-          -DWarpX_PARTICLE_PRECISION=DOUBLE
-        cmake --build build_EB -j 4
-
         ccache -s
         du -hs ~/.cache/ccache
 
     - name: run with thread sanitizer
       run: |
+        # Disabling the gds/shmem component by using gds/hash instead
+        # is required to avoid issues with shared memory.
         export PMIX_MCA_gds=hash
-        export TSAN_OPTIONS='ignore_noninstrumented_modules=1'
+
+        # Archer is a data race detector for OpenMP programs.
+        # It is required to avoid false positives with OpenMP and it is
+        # included in llvm. However with many Linux it is necessary
+        # to define this environment variable to make sure that the
+        # Archer library is actually used.
+        # When the Archer library is used and ARCHER_OPTIONS="verbose=1",
+        # the following message should be displayed:
+        # Archer detected OpenMP application with TSan, supplying OpenMP synchronization semantics
+        export OMP_TOOL_LIBRARIES=/usr/lib/llvm-17/lib/libarcher.so
         export ARCHER_OPTIONS="verbose=1"
 
+        # This option is required to avoid false positive reports from the OpenMP runtime
+        export TSAN_OPTIONS='ignore_noninstrumented_modules=1'
+
         export OMP_NUM_THREADS=2
 
         mpirun -n 2 ./build/bin/warpx.rz Examples/Physics_applications/laser_acceleration/inputs_base_rz warpx.serialize_initial_conditions = 0
@@ -158,4 +156,4 @@ jobs:
 
         ulimit -c unlimited
 
-        mpirun -n 2 ../../../build_EB/bin/warpx.2d inputs_test_2d_embedded_circle warpx.serialize_initial_conditions = 0
+        mpirun -n 2 ../../../build/bin/warpx.2d inputs_test_2d_embedded_circle warpx.serialize_initial_conditions = 0