[OpenMP] declare target does not work for inline functions

[jdoerfert]

If an inline function is used in a target region we do not automatically compile it for the device (mark it as declare target):

https://godbolt.org/z/E4Y5dzsx5

inline void foo() {}

void test( ){
    #pragma omp target
    foo();
}

results in:

; Function Attrs: convergent
declare void @foo()

[llvmbot]

@llvm/issue-subscribers-openmp

[jdoerfert]

Even explicitly declare target inline functions are ignored:
https://godbolt.org/z/cG7c7bKaE