buildsys: use SED for create-lds

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

Makerules

@@ -303,7 +303,7 @@ define create-lds
 	$(Q)$(CC) -nostdlib -nostartfiles -shared -Wl,-z,combreloc \
 	-Wl,-z,relro -Wl,--hash-style=gnu -Wl,-z,defs \
 	-Wl,--verbose 2>&1 | LC_ALL=C \
-	sed -e '/^=========/,/^=========/!d;/^=========/d' \
+	$(SED) -e '/^=========/,/^=========/!d;/^=========/d' \
 	-e 's/\. = .* + SIZEOF_HEADERS;/& $(SYMBOL_PREFIX)_begin = . - SIZEOF_HEADERS;/' > $@.lds
 endef