The package tries to link against libspc (included in the package) using gcc, which fails miserably as libspc is in C++. One of the autoconf symbols, @PTHREAD_LIBS@ is left undefined in the xmms-plugin branch. I'll attach a patch that works for me.
Created attachment 94097 [details, diff] Fixes automake files to link with g++
Created attachment 94474 [details] xmms-spc-0.2.1-r2.ebuild Revised ebuild that applies the autoconf patch.
fixed in cvs yes the patch is right! Thanks both.