Fix CMake error for python_path_test.cc test

Fix CMake error so that python_path_test.cc test
will be compiled and run with -DPYTHON3=on.

We need to conditionally compile `python_path_test.cc`. Also,
we should not call `add_subdirectory(tests)` at the beginning
because otherwise Python3_Development_FOUND will be false
when the build process enters `tests/CMakeLists.txt`.

Author: markl-arista

CMakeLists.txt

@@ -5,7 +5,6 @@ project(pstack LANGUAGES C CXX VERSION "${PSTACK_VERSION}" )
 
 include (GNUInstallDirs)
 enable_testing()
-add_subdirectory(tests)
 
 option(PYTHON3 "Compile with python 3 support" OFF)
 option(PYTHON2 "Compile with python 2 support" ON)
@@ -188,5 +187,7 @@ if (PYTHON3 AND Python3_Development_FOUND)
    add_test(NAME pydict COMMAND env PSTACK_BIN=${PSTACK_BIN}${CMAKE_CURRENT_SOURCE_DIR}/tests/pydict_test.py)
 endif()
 
+add_subdirectory(tests)
+
 # for automake and rpmbuild
 add_custom_target(check COMMAND make test)

tests/CMakeLists.txt

@@ -37,8 +37,10 @@ target_link_libraries(procself dwelf procman)
 target_link_libraries(suspend dwelf procman)
 SET_TARGET_PROPERTIES(noreturn PROPERTIES COMPILE_FLAGS "-O2 -g")
 
-add_executable(python_path_test python_path_test.cc)
-target_link_libraries(python_path_test procman dwelf)
+if (Python3_Development_FOUND OR Python2_Development_FOUND)
+   add_executable(python_path_test python_path_test.cc)
+   target_link_libraries(python_path_test procman dwelf)
+endif()
 
 add_custom_command(
    OUTPUT basic-no-unwind-gen