Add IMPORTED_IMPLIB property to each CMake Module

[y-guyon]

Apply cmake-format.

Fixes #2423.

[wantehchang]

Yannis: Thank you for writing a fix. Note that this comment is just a comment, not a request for change.

According to CMake documentation, IMPORTED_LOCATION is the pathname of the DLL and IMPORTED_IMPLIB is the pathname of the import library. So the file names are different (.dll vs. .lib) and the files may be installed in different subdirectories (bin vs. lib, as @vtorri noted in #2423 (comment)).

Perhaps the CMake documentation about this is incomplete and setting IMPORTED_LOCATION and IMPORTED_IMPLIB to the same value also works. Perhaps setting IMPORTED_IMPLIB to the pathname of some file is better than not setting it. I don't know. I am just reporting what I found in the CMake documentation.

Here are the relevant excerpts:

https://cmake.org/cmake/help/latest/prop_tgt/IMPORTED_LOCATION.html

IMPORTED_LOCATION

Full path to the main file on disk for an IMPORTED target.

Set this to the location of an IMPORTED target file on disk. [...] For DLLs this is the location of the .dll part of the library. [...]

https://cmake.org/cmake/help/latest/prop_tgt/IMPORTED_IMPLIB.html

IMPORTED_IMPLIB

Full path to the import library for an IMPORTED target.

This property may be set:

• On DLL platforms, to the location of the .lib part of the DLL.

https://cmake.org/cmake/help/latest/guide/importing-exporting/index.html#importing-libraries

On Windows, a .dll and its .lib import library may be imported together:

add_library(bar SHARED IMPORTED)
set_property(TARGET bar PROPERTY
             IMPORTED_LOCATION "c:/path/to/bar.dll")
set_property(TARGET bar PROPERTY
             IMPORTED_IMPLIB "c:/path/to/bar.lib")
add_executable(myexe src1.c src2.c)
target_link_libraries(myexe PRIVATE bar)

[wantehchang]

I found a comment in a CMake issue that apparently matches what @vtorri reported in #2423 (comment) and explains why this pull request works:

https://gitlab.kitware.com/cmake/cmake/-/issues/22446#note_1444129

On a related note, MinGW can directly link with DLLs, without the need for an import library. It would be great if, when building with a MinGW toolchain, IMPORTED_IMPLIB were optional and IMPORTED_LOCATION were used if it is absent. (As a workaround, specifying the path to the DLL as IMPORTED_IMPLIB seems to work, but only by accident.)

[y-guyon]

Thank you for investigating.