openscenegraph: enable parallel building

+2
+2
pkgs/development/libraries/openscenegraph/default.nix
··· 20 20 pkgconfig kbproto SDL qt4 poppler librsvg gtk 21 21 ]; 22 22 23 + enableParallelBuilding = true; 24 + 23 25 cmakeFlags = [ 24 26 "-DMATH_LIBRARY=" 25 27 "-DCMAKE_C_FLAGS=-D__STDC_CONSTANT_MACROS=1"