WIP: fix dotnet not found on mono #30

Job	Run time
macOS--mono	34s
linux-newLTS-vanilla--dotnet6	9m 19s
linux-newLTS-github--dotnet-and-msbuild	9m 14s
linux-newLTS-github--dotnet-and-xbuild	9m 18s
linux-newLTS-vanilla--newmono	2m 8s
linux-newLTS-vanilla--stockmono	1m 6s
linux-oldLTS-github--dotnet-and-msbuild	7m 47s
linux-oldLTS-github--dotnet-and-xbuild	7m 42s
linux-oldLTS-vanilla--newmono	2m 24s
linux-oldLTS-vanilla--stockmono	1m 41s
macOS--dotnet6-and-mono	12m 8s
windows--dotnet6	9m 31s
windows--legacyFramework	3m 30s
sanity-check	0s
publish	0s
	1h 16m 22s

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