Update build.sh to use dnvm correctly.

build.sh

@@ -27,7 +27,7 @@ if test ! -d packages/KoreBuild; then
     mono .nuget/nuget.exe install Sake -version 0.2 -o packages -ExcludeVersion
 fi
 
-if ! type k > /dev/null 2>&1; then
+if ! type dnvm > /dev/null 2>&1; then
     source packages/KoreBuild/build/dnvm.sh
 fi
 
@@ -36,3 +36,4 @@ if ! type k > /dev/null 2>&1; then
 fi
 
 mono packages/Sake/tools/Sake.exe -I packages/KoreBuild/build -f makefile.shade "$@"
+