jl_setjmp is not exported on Windows by the LTS version

[Taaitaaiger]

Sorry for not noticing this sooner despite opening an issue about it before, but on Windows jl_setjmp is not exported by the LTS version. As a result the JL_TRY and JL_CATCH macros can't be used when embedding Julia.

#42245

[IanButterworth]

There are also some jl_setjmp redefinition warnings on master, at least on MacOS

    CC src/llvm-pass-helpers.o
In file included from /Users/ian/Documents/GitHub/julia/src/llvm-pass-helpers.cpp:18:
./jl_internal_funcs.inc:513:9: warning: 'jl_setjmp' macro redefined [-Wmacro-redefined]
#define jl_setjmp ijl_setjmp
        ^
./julia.h:1908:9: note: previous definition is here
#define jl_setjmp(a,b) sigsetjmp(a,b)
        ^
1 warning generated.
    CC src/llvm-late-gc-lowering.o

[JeffBezanson]

#42267 should be backported