'-w' option given to destroot.cmd even though it is not gmake

[j-macports@…]

Using MacPorts base trunk (r91709). Trying to install npm @1.1.15 :

$ sudo port install npm
--->  Computing dependencies for npm
--->  Fetching archive for npm
--->  Attempting to fetch npm-1.1.15_0.darwin_11.noarch.tbz2 from http://packages.macports.org/npm
--->  Fetching distfiles for npm
--->  Attempting to fetch npm-1.1.15.tgz from http://lil.fr.distfiles.macports.org/npm
--->  Verifying checksum(s) for npm
--->  Extracting npm
--->  Applying patches to npm
--->  Configuring npm
--->  Building npm
--->  Staging npm into destroot
Error: No files have been installed in the destroot directory!
Error: Please make sure that this software supports 'make install DESTDIR=${destroot}' or implement an alternative destroot mechanism in the Portfile.
Error: Files might have been installed directly into your system, check before proceeding.
Error: org.macports.destroot for port npm returned: Staging npm into destroot failed
Please see the log file for port npm for details:
    /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_devel_npm/npm/main.log
To report a bug, follow the instructions in the guide:
    http://guide.macports.org/#project.tickets
Error: Processing of port npm failed

Looking at the log, it appears a '-w' option has been added to the port's destroot.cmd, even though it is not gmake :

destroot.cmd        ${prefix}/bin/node ./cli.js

MacPorts 2.0.4 works fine.

The regression seems to have been introduced in r90650.

[j-macports@…]

Proposed fix, with unit tests

[neverpanic (Clemens Lang)]

Thanks for the patch and the test, r91744.