Don't parallelize builds on non-Linux platforms for code coverage builds.
Don't parallelize builds on non-Linux platforms for code coverage builds.

Some of the Mac CI workers don't have sufficient memory to handle
parallel builds without paging.

realm/realm-object-store,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-core,realm/realm-object-store,realm/realm-core,realm/realm-core,realm/realm-object-store