问题
I know that when I am in a function, I can set the variable in the calling scope by using:
set(MYVAR 1 PARENT_SCOPE)
What I want is to be able to set a variable in the grandparent scope (if it exists).
I know that if I redefine my function as a macro, then set(MYVAR 1 PARENT_SCOPE) effectively does what I need. But unfortunately, I cannot do that for unrelated reasons.
A solution would work for me as a walkaround for the problem in How to check if the variable is set in the parent scope, (as opposed to being inherited from grandparents) in CMake? .
来源：https://stackoverflow.com/questions/56295714/how-to-write-a-variable-to-the-parents-parent-scope-in-cmake