added error messages if some attempts to build a row major variant
added error messages if some attempts to build a row major variant

maxhutch/libxsmm,hfp/libxsmm,egeor/libxsmm,hfp/libxsmm,egeor/libxsmm,egeor/libxsmm,hfp/libxsmm,hfp/libxsmm,maxhutch/libxsmm,egeor/libxsmm,hfp/libxsmm,hfp/libxsmm,egeor/libxsmm,maxhutch/libxsmm,maxhutch/libxsmm,egeor/libxsmm