CMake: fix MIGRATE_MODULE matching syntax (remove backslash line-continuation)

CMakeLists.txt

@@ -346,12 +346,7 @@ function(NGL_ADD_SUBDIR_GUARDED subdir)
     # If MIGRATE_MODULE either starts with the subdir, equals it, contains it as a path component,
     # or the basename matches, include the subdir. This makes nested paths like
     # 'Lts/Proxies/TrainingAreaBase' include both 'Lts' and its child 'Proxies'.
-    if(_mig MATCHES "^${_sub}(/|$)" \
-       OR _sub MATCHES "^${_mig}(/|$)" \
-       OR _mig MATCHES ".*/${_sub}(/|$)" \
-       OR _sub MATCHES ".*/${_mig}(/|$)" \
-       OR _mig_base STREQUAL _sub \
-       OR _sub_base STREQUAL _mig)
+    if(_mig MATCHES "^${_sub}(/|$)" OR _sub MATCHES "^${_mig}(/|$)" OR _mig MATCHES ".*/${_sub}(/|$)" OR _sub MATCHES ".*/${_mig}(/|$)" OR _mig_base STREQUAL _sub OR _sub_base STREQUAL _mig)
       message(STATUS "Including subdir ${subdir} because MIGRATE_MODULE=${MIGRATE_MODULE}")
       add_subdirectory(${subdir})
     else()