Export jl_debug_method_invalidation.

[maleadt]

Seems useful, ref #35714

julia> f() = 1
f (generic function with 1 method)

julia> f()
1

julia> f() = 2
f (generic function with 1 method)

julia> f()
2

julia> unsafe_store!(cglobal(:jl_debug_method_invalidation, Cint), 1)
Ptr{Int32} @0x00007ff48d312260

julia> f() = 3
-- f()
f (generic function with 1 method)

julia> f()
3

[timholy]

SnoopCompile support will land shortly after this merges, see timholy/SnoopCompile.jl#77.