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At the time of writing, clang version 13.0.0 is known to work for building flang. The flang binary obtained from main does not have support for code generation yet. A prototype for this exists in the fir-dev branch and should be upstreamed in the hopefully near future. However, even a flang built from the fir-dev branch is not currently capable of compiling a hello world on Windows on Arm. Part of the issue is that the flang driver does not add all the runtime libraries needed on Windows. Current progress towards that goal is tracked in Jira.