Add -Z small-data-threshold
This flag allows specifying the threshold size above which LLVM should not consider placing small objects in a `.sdata` or `.sbss` section.
Support is indicated in the target options via the
small-data-threshold-support target option, which can indicate either an
LLVM argument or an LLVM module flag. To avoid duplicate specifications
in a large number of targets, the default value for support is
DefaultForArch, which is translated to a concrete value according to the
target's architecture.
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