libtool: respect environment variables
libtool: respect environment variables

The /usr/bin/libtool script used to use cross tool-chains,
when it was cross compiled.
This broke cross-built libtool for native builds and was changed in
653f4339274d162109af27c93a741264460f2da4 to native tool-chains.
Setting native tool-chains in libtools causes cross-builds which use
libtool to fail.

Thus, change /usr/bin/libtool to use environment variables when defined
and fall back to the native tool-chain otherwise.

necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages