ci: Lower the number or parallel compilations

Author: chfast

circle.yml

@@ -390,7 +390,7 @@ jobs:
   sanitizers-gcc:
     executor: linux-gcc-latest
     environment:
-      CMAKE_BUILD_PARALLEL_LEVEL: 6
+      CMAKE_BUILD_PARALLEL_LEVEL: 2
       # TODO: Enable detect_stack_use_after_return=1 when https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97414 is fixed.
       ASAN_OPTIONS: detect_invalid_pointer_pairs=2:check_initialization_order=1
       UBSAN_OPTIONS: halt_on_error=1