fsx,fsxc: fix PrintUsage() to identify program #1553

Job	Run time
linux-oldLTS-github--dotnet-and-msbuild	7m 36s
macOS--mono	10m 24s
linux-oldLTS-github--dotnet-and-xbuild	7m 16s
macOS--dotnet6-and-mono	10m 18s
linux-newLTS-vanilla--stockmono	7m 33s
linux-newLTS-github--dotnet-and-msbuild	9m 14s
linux-newLTS-github--dotnet-and-xbuild	10m 39s
linux-oldLTS-vanilla--newmono	6m 46s
linux-oldLTS-vanilla--stockmono	6m 34s
linux-newLTS-vanilla--dotnet6	8m 44s
linux-newLTS-vanilla--newmono	6m 37s
windows--dotnet6	12m 51s
windows--legacyFramework	16m 12s
sanity-check	57s
publish	0s
	2h 1m 41s

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