POSIX::strftime: Mark args as unused #13515

Job	Run time
Sanity: Linux -Dusethreads	10m 13s
involved_authors_debug	0s
macOS (Monterey) 12 (-Uusethreads)	12m 54s
linux (-Uusethreads)	9m 44s
macOS (Monterey) 12 (-Duseithreads -Duseshrplib)	15m 43s
linux (-Duseshrplib -Dusequadmath -Dusecbacktrace -Dusethreads)	11m 18s
cygwin	33m 18s
install	10m 33s
linux (-Duserelocatableinc)	9m 31s
linux (-Dcc='clang')	10m 23s
linux i386/ubuntu (-Dusedevel)	15m 45s
Windows mingw64	34m 36s
linux (-Dcc='g++')	9m 41s
minitest	3m 37s
linux (-Accflags=-DSILENT_NO_TAINT_SUPPORT)	9m 41s
Windows msvc142	51m 49s
linux (-Accflags=-DNO_TAINT_SUPPORT)	9m 35s
linux (-DDEBUGGING -Accflags=-DPERL_RC_STACK)	10m 9s
ASAN (-Accflags=-DPURIFY)	21m 3s
dist-modules (latest)	2m 19s
ASAN (-DDEBUGGING)	22m 30s
dist-modules (5.24)	2m 19s
ASAN (-Dusethreads)	22m 37s
dist-modules (5.10)	2m 16s
linux (-Uusedl)	9m 6s
dist-modules (5.8)	2m 20s
Test dist/ modules on MacOS system perl	4m 23s
PERL_UNICODE (-Uusethreads)	8m 21s
PERL_UNICODE (-Dusethreads -Accflags=-DPURIFY -Dcc='gcc -fsanitize=address' -Dld='gcc -fsanitize=...	25m 31s
	6h 31m 15s

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