druntime: -debug=PRINTF compilation fix

[denizzzka]

No description provided.

[github-actions]

DMD perf check

Metric	Base	PR	delta
compile hello.d (instr)	215.9 M	215.9 M	0.00%
compile hello.d -O (instr)	234.5 M	234.5 M	0.00%
compile Phobos (instr)	5,078.9 M	5,077.3 M	-0.03%
compile Phobos codegen (instr)	1,454.8 M	1,453.1 M	-0.12%
compile vibe.d (instr)	15,136.8 M	15,136.7 M	0.00%
dmd binary size (stripped)	6.92 MB	6.92 MB	0.00%
hello binary size	0.72 MB	0.72 MB	0.00%
peak RSS (compile hello.d)	44 MB	44 MB	-0.10%
peak RSS (compile Phobos)	632 MB	633 MB	+0.14%
peak RSS (compile vibe.d)	1981 MB	1981 MB	+0.02%