Fix gdc-12 build #285

Job	Run time
Run all tests (dmd-latest, dmd, ubuntu-22.04, make)	3m 1s
Run all tests (dmd-latest, dmd, ubuntu-22.04, dub, min libdparse)	1m 33s
Run all tests (dmd-latest, dmd, macos-latest, make)	4m 10s
Run all tests (dmd-latest, dmd, macos-latest, dub, min libdparse)	3m 15s
Run all tests (dmd-latest, dmd, windows-latest, make)	4m 0s
Run all tests (dmd-latest, dmd, windows-latest, dub, min libdparse)	3m 0s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, make)	3m 20s
Run all tests (ldc-latest, ldmd2, ubuntu-22.04, dub, min libdparse)	2m 2s
Run all tests (ldc-latest, ldmd2, macos-latest, make)	12m 6s
Run all tests (ldc-latest, ldmd2, macos-latest, dub, min libdparse)	3m 41s
Run all tests (ldc-latest, ldmd2, windows-latest, make)	8m 7s
Run all tests (ldc-latest, ldmd2, windows-latest, dub, min libdparse)	3m 27s
Run all tests (dmd-latest, gdc-12, ubuntu-22.04, make)	5m 5s
	56m 47s

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