make.sh: Fix checksum generation of the toolchain once again

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

make.sh

@@ -1240,14 +1240,21 @@ compress_toolchain() {
 		return 1
 	fi
 
+	# Change to the temporary directory
+	pushd "${tmp}" &>/dev/null
+
 	# Create the checksums
-	if ! cd "${tmp}" && b2sum "${toolchain}" > "${tmp}/${checksums}"; then
+	if ! b2sum "${toolchain}" > "${tmp}/${checksums}"; then
+		popd &>/dev/null
+
 		# Cleanup
 		rm -rf "${tmp}"
 
 		return 1
 	fi
 
+	popd &>/dev/null
+
 	# Everything is good, move the files to their destination
 	if ! mv \
 			"${tmp}/${toolchain}" \