IN_TRY_COMPILE
From Get docs
Cmake/docs/3.21/prop gbl/in try compile
IN_TRY_COMPILE
Read-only property that is true during a try-compile configuration.
True when building a project inside a try_compile() or try_run() command.
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https://cmake.org/cmake/help/v3.21/prop_gbl/IN_TRY_COMPILE.html