perf: optimize cpp target generation #668

Job	Run time
pre-commit	21s
consistency	13s
check • x64-linux • gcc-13 • c++20 • Debug	2m 12s
check • x64-windows • msvc-2022 • c++20 • Debug	4m 11s
check • x64-linux • gcc-13 • c++20 • RelWithDebInfo	2m 22s
check • x64-windows • msvc-2022 • c++20 • RelWithDebInfo	5m 6s
check-auto-detect-triplet	2m 8s
check • x64-linux • llvm-17 • c++20 • Debug	3m 5s
check-auto-vcpkg-install	1m 39s
check • x64-windows • llvm-17 • c++20 • Debug	3m 48s
check • x64-windows • llvm-17 • c++20 • RelWithDebInfo	3m 52s
Docs build and checks	2m 2s
check • x64-linux • llvm-17 • c++20 • RelWithDebInfo	2m 15s
check-export-mode	1m 47s
check • x64-mingw-dynamic • mingw • c++20 • Debug	5m 27s
codecov	2m 9s
check • x64-mingw-dynamic • mingw • c++20 • RelWithDebInfo	6m 31s
check • x64-osx • gcc-13 • c++20 • Debug	3m 38s
check • x64-osx • gcc-13 • c++20 • RelWithDebInfo	3m 34s
check • x64-osx • llvm@17 • c++20 • Debug	3m 5s
check-auto-build-type	1m 45s
check • x64-osx • llvm@17 • c++20 • RelWithDebInfo	3m 22s
pass	2s
release	0s
	1h 4m 34s

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