If a user wishes to build pyrogenesis with support for Valgrind (such as it is), then can now do so by passing --with-valgrind to update-workspaces.sh. (They will need Valgrind installed and locateable via pkg-config.)
According to the Valgrind website, they don't - and probably never will - support Windows systems, so I've also made it non-Windows option.
Since Alpha 16, Fedora has patched our extern_libs.lua file to use their repo-supplied Valgrind (to resolve https://bugzilla.redhat.com/show_bug.cgi?id=1141464). Now, they won't have to.
 - https://valgrind.org/info/platforms.html, "Porting Plans"