cmake: restore a "exiv2lib" target (backport #2832) #1020

Job	Run time
Linux-GCC7-deps=forcefallback	1m 37s
Linux-Clang7-deps=forcefallback	1m 46s
Linux-GCC7-deps=default	1m 23s
Linux-Clang7-deps=default	1m 13s
Linux-GCC13-deps=forcefallback	2m 43s
Linux-Clang17-deps=forcefallback	2m 46s
Linux-GCC13-deps=default	1m 58s
Linux-Clang17-deps=default	2m 6s
Emscripten	2m 40s
FreeBSD	6h 0m 3s
macOS-deps=enabled	1m 25s
macOS-deps=disabled	2m 14s
MSYS2-UCRT64-deps=enabled	5m 12s
MSVC-forcefallback-x64	4m 4s
MSYS2-CLANG32-deps=enabled	3m 57s
MSVC-forcefallback-x86	4m 40s
MSYS2-CLANG64-deps=enabled	4m 31s
clang-cl-forcefallback	4m 44s
MSVC-default-x64	2m 8s
MSYS2-UCRT64-deps=disabled	6m 4s
clang-cl-default	4m 14s
MSYS2-CLANG32-deps=disabled	6m 4s
MSVC-default-x86	2m 35s
MSYS2-CLANG64-deps=disabled	5m 42s
	7h 15m 49s

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