build: use `-march=haswell` when testing dpdk build on github-hosted … #84

Job	Run time
Tests (clang++-18, C++20, dev, )	18m 34s
Tests (clang++-18, C++20, debug, )	17m 18s
Tests (clang++-18, C++20, release, )	17m 50s
Tests (clang++-18, C++23, dev, )	18m 44s
Tests (clang++-18, C++23, debug, --enable-cxx-modules)	14m 11s
Tests (clang++-18, C++23, release, --enable-dpdk)	24m 35s
Tests (gcc-13, C++20, dev, )	12m 43s
Tests (gcc-13, C++20, debug, )	19m 40s
Tests (gcc-13, C++20, release, )	18m 10s
Tests (gcc-13, C++23, dev, )	18m 49s
Tests (gcc-13, C++23, debug, )	20m 20s
Tests (gcc-13, C++23, release, )	23m 6s
	3h 44m 0s

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