cmd/ld: explicitly ignore R_*_NONE relocation to fix build

        I don't know why this relocation is used.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6464070

src/cmd/ld/ldelf.c

@@ -658,6 +658,8 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
 					p += 4;
 				}
 			}
+			if(info & 0xffffffff == 0) // R_*_NONE relocation
+				continue;
 			if((info >> 32) == 0) { // absolute relocation, don't bother reading the null symbol
 				rp->sym = S;
 			} else {