* for a --target argument that precedes the compiler argument, as in:
slibtool --target=xxx --mode=compile cc
--> set an explicit (cross-)target,
--> but do not pass the argument to the compiler.
* for a --target argument that follows the compiler argument, as in:
slibtool --mode=compile cc --target=xxx
--> set an explicit (cross-)target,
--> and also pass the argument to the compiler.
When no -rpath argument is provided we cannot build a dynamic
library. To match gnu libtool's behavior, build in this case a
static library even if -disable-static has been specified.
