Allow LD_LIBRARY_PATH override for python tests

On some HPC toolchains, a third-party Python package imported before
ecflow (for example numpy) resolves and loads the platform default
libstdc++ first. Since ELF soname resolution is process-wide and
first-one-wins, this can leave ecflow.so unable to satisfy the GLIBCXX
symbol version it was actually built against, when the build toolchain
differs from the platform default.

Add ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH, a configure-time cache
variable that prepends a given runtime library directory to
LD_LIBRARY_PATH for the py3_u_* and py3_s_* tests, so the correct
libstdc++.so.6 is resolved regardless of which component asks for it
first. Left empty by default, leaving unaffected platforms untouched.

Wire the new flag into the gnu-15.2.0 and gnu-14.2.0 HPC CI jobs in
.github/ci-hpc-config.yml, pointing at each toolchain's libstdc++
directory, so the affected python tests actually pass in CI.

Author: marcosbento

.github/ci-hpc-config.yml

@@ -37,6 +37,7 @@ gnu-15.2.0:
         -DPython3_LIBRARIES=/usr/local/apps/python3/3.13.13-01/lib64/libpython3.13.so
         -DPython3_LIBRARY_DIRS=/usr/local/apps/python3/3.13.13-01/lib64
         -DCMAKE_PREFIX_PATH=/usr/local/apps/python3/3.13.13-01/lib/python3.13/site-packages/pybind11/share/cmake/pybind11
+        -DECFLOW_PYEXT_TEST_LD_LIBRARY_PATH=/usr/local/apps/gcc/15.2.0/lib64
       # Note: Python 3.13.13-01, provides Pybind11 3.0.4.
     ctest_options:
       # disable s_http* tests
@@ -65,6 +66,7 @@ gnu-14.2.0:
         -DPython3_LIBRARIES=/usr/local/apps/python3/3.12.9-01/lib64/libpython3.12.so
         -DPython3_LIBRARY_DIRS=/usr/local/apps/python3/3.12.9-01/lib64
         -DCMAKE_PREFIX_PATH=/usr/local/apps/python3/3.13.13-01/lib/python3.13/site-packages/pybind11/share/cmake/pybind11
+        -DECFLOW_PYEXT_TEST_LD_LIBRARY_PATH=/usr/local/apps/gcc/14.2.0/lib64
       # Note: Python 3.13.13-01, provides Pybind11 3.0.4.
       #
       # Important:

libs/pyext/python3/CMakeLists.txt

@@ -68,16 +68,42 @@ set_target_properties(ecflow3
 # with 'No module named pytest'.
 execute_process(
   COMMAND ${Python3_EXECUTABLE} -c "import pytest"
-  RESULT_VARIABLE _ecflow_have_pytest
+  RESULT_VARIABLE _ECFLOW_HAVE_PYTEST
   OUTPUT_QUIET ERROR_QUIET)
-if( NOT _ecflow_have_pytest EQUAL 0 )
+if( NOT _ECFLOW_HAVE_PYTEST EQUAL 0 )
   message( WARNING
     "pytest was not found for ${Python3_EXECUTABLE}; the python tests "
     "(py3_u_* and py3_s_*) will fail to run. Install it with:\n"
     "    ${Python3_EXECUTABLE} -m pip install -r "
     "${CMAKE_CURRENT_SOURCE_DIR}/../test/requirements-test.txt" )
 endif()
 
+#
+# When using some HPC toolchains, the dynamic linker for ecflow resolves and loads the platform default libstdc++ first,
+# instead of the one that ecflow.so was built against. This leads to symbol version mismatches, and the python tests
+# fail with errors like:
+#
+#   /lib64/libstdc++.so.6: error: version lookup error: version `GLIBCXX_3.4.32' not found
+#     (required by /path/to/ecflow/build/libs/pyext/python3/ecflow.so) (fatal)
+#
+# ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH allows a runtime library directory to be prepended to LD_LIBRARY_PATH, so that
+# the correct libstdc++.so.6 is used by the python tests.
+#
+set(ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH "" CACHE STRING
+  "Colon-separated directories prepended to LD_LIBRARY_PATH when running the python tests")
+
+set( _ECFLOW_PYEXT_ENVIRONMENT
+  "PATH=${Python3_EXECUTABLE_DIR}:$ENV{PATH}"
+  "PYTHONPATH=${ECFLOW_PYTHONPATH}"
+)
+if( ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH )
+  if( DEFINED ENV{LD_LIBRARY_PATH} AND NOT "$ENV{LD_LIBRARY_PATH}" STREQUAL "" )
+    list( APPEND _ECFLOW_PYEXT_ENVIRONMENT "LD_LIBRARY_PATH=${ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH}:$ENV{LD_LIBRARY_PATH}" )
+  else()
+    list( APPEND _ECFLOW_PYEXT_ENVIRONMENT "LD_LIBRARY_PATH=${ECFLOW_PYEXT_TEST_LD_LIBRARY_PATH}" )
+  endif()
+endif()
+
 foreach( test ${u_tests} )
   ecbuild_add_test(
     TARGET
@@ -88,7 +114,7 @@ foreach( test ${u_tests} )
     ARGS
       -m pytest ${CMAKE_CURRENT_SOURCE_DIR}/../test/py_${test}.py -v
     ENVIRONMENT
-      "PATH=${Python3_EXECUTABLE_DIR}:$ENV{PATH};PYTHONPATH=${ECFLOW_PYTHONPATH}"
+      ${_ECFLOW_PYEXT_ENVIRONMENT}
     TEST_DEPENDS
       u_base
   )
@@ -97,6 +123,11 @@ endforeach()
 
 if ( ENABLE_ALL_TESTS AND ENABLE_SERVER)
 
+  #
+  # Python integration tests run the ecflow server, and thus use ECF_SSL_DIR to find the generated SSL certificates.
+  #
+  list( APPEND _ECFLOW_PYEXT_ENVIRONMENT "ECF_SSL_DIR=${CMAKE_CURRENT_BINARY_DIR}/" )
+
   foreach( test ${s_tests} )
     ecbuild_add_test(
       TARGET
@@ -107,7 +138,7 @@ if ( ENABLE_ALL_TESTS AND ENABLE_SERVER)
       ARGS
         -m pytest ${CMAKE_CURRENT_SOURCE_DIR}/../test/py_${test}.py -v
       ENVIRONMENT
-        "PATH=${Python3_EXECUTABLE_DIR}:$ENV{PATH};PYTHONPATH=${ECFLOW_PYTHONPATH};ECF_SSL_DIR=${CMAKE_CURRENT_BINARY_DIR}/"
+        ${_ECFLOW_PYEXT_ENVIRONMENT}
       TEST_DEPENDS
         u_base
     )