ponyc

Split PR workflow into three independent workflows #1

Job	Run time
x86-64 Apple Darwin	1m 35s
arm64 Apple Darwin	1s
arm64 Linux musl	1m 25s
riscv64 Linux glibc	1m 25s
arm64 Linux glibc	1m 19s
arm Linux glibc	1s
armhf Linux glibc	1m 25s
x86-64 Linux glibc	1m 25s
arm64 Windows MSVC	1m 32s
x86-64 Windows MSVC	1m 25s
x86-64 Linux musl	1s
use ${{ matrix.directives }}	1s
with sanitizers ${{ matrix.directives }}	1s
	11m 36s

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