macro processor: simplify handling of `@#define`

6 jobs for master in 2 minutes and 34 seconds (queued for 6 seconds)
Status Job ID Name Coverage
  Build
passed #14067
build_linux_32

00:00:51

passed #14068
build_linux_64

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passed #14071
macOS
build_macOS

00:02:26

passed #14069
build_windows_32

00:01:39

passed #14070
build_windows_64

00:01:37

 
  Prepare
passed #14072
aggregate_builds

00:00:05