Unbuffered mode for Python subprocesses

tools/ci.py

     print('Running bootstrap')
     subprocess.check_call([
         sys.executable,
-        TOOLS_DIR / 'bootstrap.py',
+        '-u',
+        str(TOOLS_DIR / 'bootstrap.py'),
         f'--cxx={opts.cxx}',
     ])
 
         _do_bootstrap(opts)
 
     subprocess.check_call([
-        PREBUILT_DDS,
+        str(PREBUILT_DDS),
         'deps',
         'build',
         f'-T{opts.toolchain}',
     ])
 
     subprocess.check_call([
-        PREBUILT_DDS,
+        str(PREBUILT_DDS),
         'build',
         '--full',
         f'-T{opts.toolchain}',
 
     subprocess.check_call([
         sys.executable,
-        TOOLS_DIR / 'test.py',
+        '-u',
+        str(TOOLS_DIR / 'test.py'),
         f'--exe={PROJECT_ROOT / "_build/dds"}',
         f'-T{opts.toolchain}',
     ])