Fix CMake build

[H1X4Dev]

After the change in 81629e4, seems like it broke CMake builds when using CPM, this pull request fixes that.

1> [CMake] CMake Error at out/build/x64-Debug/_deps/fmt-src/CMakeLists.txt:55 (target_sources):
1> [CMake]   Cannot find source file:
1> [CMake] 
1> [CMake]     README.rst
1> [CMake] Call Stack (most recent call first):
1> [CMake]   out/build/x64-Debug/_deps/fmt-src/CMakeLists.txt:285 (add_module_library)
1> [CMake] CMake Error at out/build/x64-Debug/_deps/fmt-src/CMakeLists.txt:50 (add_library):
1> [CMake]   No SOURCES given to target: fmt
1> [CMake] Call Stack (most recent call first):
1> [CMake]   out/build/x64-Debug/_deps/fmt-src/CMakeLists.txt:285 (add_module_library)
1> [CMake] CMake Generate step failed.  Build files cannot be regenerated correctly.

[vitaut]

Thanks for the PR! Could you also update line 451?

[dde-cls]

I opened this related issue: #3742

I suppose it just boils down to rectify the reference in CMakeLists.txt, line 286.

[vitaut]

Could you also update line 451?

Nevermind, I applied the change locally. Merged in 4497a2d.