Introduce explicit iterate_over field for flag_group in Crosstool
Now flag_group can be marked with iterate_over field, that denotes for which
sequence variable the flag_group will be expanded repeatedly. This cl does that
in backwards compatible way as before, the iteration happened implicitly when the
used variable was found to be sequence at runtime. Because of that it adds some
extra code that will be removed once all the crosstools are migrated to the
explicit iteration.
RELNOTES: NONE
PiperOrigin-RevId: 138501033
1 file changed
