Only set CMAKE_EXECUTABLE_SUFFIX in toolchain if not defined already

[starball5]

Fixes #18860

[sbc100]

Change LGTM, but can you add a test for this (i.e. update one of the existing cmake tests so that it will fail without this change).

[sbc100]

Looks like the test-other failures are geniune.

[aviallon]

Is that still needed, or should this be closed?

[sbc100]

@starball5 would you have time to rebase and add a test? Or should someone else take a look?

[sbc100]

I tried to pick up this PR but I noticed that -DCMAKE_EXECUTABLE_SUFFIX=xx does not work from the command line ,even after this PR. It also doesn't work from the command line for native / host projects.

However, -DCMAKE_EXECUTABLE_SUFFIX_<LANG>=xx , does work. So I created a PR to test this: #26244.

Its unfortunate that -DCMAKE_EXECUTABLE_SUFFIX does not work but it seems to be a limitation of cmake and not emscripten.

@bradking maybe can you explain this seemingly behavior?

[bradking]

CMAKE_EXECUTABLE_SUFFIX was not designed to be set by end users or in the cache. It's normally set by the platform modules or toolchain files. If it needs to be changed for some use case, that needs to be modeled with other options such that the platform module knows to set the needed value.

[bradking]

if(NOT DEFINED CMAKE_EXECUTABLE_SUFFIX) may never be true because CMake's Modules/CMakeGenericSystem.cmake always sets a default empty value earlier. Therefore this change may regress the existing default.

[sbc100]

Thanks @bradking. I suppose emscripten is a little strange in that we support different output file suffixes and each one comes with different output behaviour so users often want to set the output suffix themselves.

I think this PR can be closed than.

I might still try to land #26244.