win,build: forward release_urlbase to configure

The RELEASE_URLBASE environment variable is used in releases as
a prefix for links in the process.release object. The Makefile picks
it and forwards it to configure, but vcbuild.bat did not. Hence, in
Windows, Node releases have a correct process.release because it uses
the default URL, but nightlies, RCs and so on do not, breaking
node-gyp. This enables native modules to be built with such versions
of Node.

PR-URL: nodejs#8430
Reviewed-By: jbergstroem - Johan Bergström <bugs@bergstroem.nu>

vcbuild.bat

@@ -33,7 +33,6 @@ set noperfctr=
 set noperfctr_msi_arg=
 set i18n_arg=
 set download_arg=
-set release_urls_arg=
 set build_release=
 set enable_vtune_arg=
 set configure_flags=
@@ -107,7 +106,7 @@ if "%config%"=="Debug" set configure_flags=%configure_flags% --debug
 if defined nosnapshot set configure_flags=%configure_flags% --without-snapshot
 if defined noetw set configure_flags=%configure_flags% --without-etw& set noetw_msi_arg=/p:NoETW=1
 if defined noperfctr set configure_flags=%configure_flags% --without-perfctr& set noperfctr_msi_arg=/p:NoPerfCtr=1
-if defined release_urlbase set release_urlbase_arg=--release-urlbase=%release_urlbase%
+if defined release_urlbase set configure_flags=%configure_flags% --release-urlbase=%release_urlbase%
 if defined download_arg set configure_flags=%configure_flags% %download_arg%
 if defined enable_vtune_arg set configure_flags=%configure_flags% --enable-vtune-profiling
 if defined dll set configure_flags=%configure_flags% --shared