Fix bad paths in top-level Makefile

Makefile

@@ -25,8 +25,8 @@ UPDATE:
 	#@make -C Kernel/ UPDATE --no-print-directory
 	#@make -C Kernel/ ../libcore/lib.rs --no-print-directory
 	#
-	@mkdir -p ../.prefix
-	curl https://static.rust-lang.org/rustup/rustup-init.sh -sSf | RUSTUP_HOME=$(abspath ../.prefix) CARGO_HOME=$(abspath ../.prefix) sh -s -- --default-toolchain none --no-modify-path -y
+	@mkdir -p .prefix
+	curl https://static.rust-lang.org/rustup/rustup-init.sh -sSf | RUSTUP_HOME=$(abspath .prefix) CARGO_HOME=$(abspath .prefix) sh -s -- --default-toolchain none --no-modify-path -y
 	$(call fn_rustcmd,rustup) update $(RUSTUP_VER)
 	$(call fn_rustcmd,rustup) default $(RUSTUP_VER)
 	#$(call fn_rustcmd,rustup) component add rust-src