Discourage building with MSBUILDDEBUGONSTART (#4952)
Discourage building with MSBUILDDEBUGONSTART (#4952)

Discourage building with MSBUILDDEBUGONSTART. Allow debugging of a build if MSBUILDDEBUGONSTART_HARD is defined.
sean-gilliam/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,mono/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,cdmihai/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,mono/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,mono/msbuild,mono/msbuild,cdmihai/msbuild