Vim version: 8.1
OS: macOS Mojave 10.14.3

I am using the flag -MMD to generate dependency files to determine when a header has been changed. Since more compiler flags are now being parsed this flag causes a file with the name of -.d to be generated in the working directory.

I believe this is related to #2131 (possibly #2168 or #2194).

This flag should be ignored since it doesn't provide any useful linting information.

Thanks!