Files with more than one period in their name are not properly named when split

[muff1n1634]

I came across this when I was decomposing MSL; in particular, there's a file named sysenv.GCN.o as specified by some unstripped .elf files, so I added it to my splits

extern/msl/libc/embedded/sysenv.GCN.c:
	.text       start:0x804385FC end:0x80438604

but running dtk dol split (dtk/config.yml disasm) produces the following:

> ls -la disasm/obj/extern/msl/libc/embedded | grep sysenv
-rw-r--r-- 1 muffin None  540 Dec 17 15:15 sysenv.o

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reproduction

1. add a file to splits.txt with a name with multiple periods in it like a.b.c
2. split the dol
3. check filename. will probably be missing infixes

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environment

OS: Windows 10 22H2
dtk -V: dtk 0.6.4 0cfc5df20b4d03604649afb88897d4e011fc9b26