Slightly improve the bash scripts

assemble.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -euxo pipefail
 

check-blobs.sh

@@ -1,21 +1,21 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # Checks that the blobs are up to date with the committed assembly files
 
 set -euxo pipefail
 
-for lib in $(ls bin/*.a); do
-    filename=$(basename $lib)
-    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.before
+for lib in bin/*.a; do
+    filename=$(basename "$lib")
+    arm-none-eabi-objdump -Cd "$lib" > "bin/${filename%.a}.before"
 done
 
 ./assemble.sh
 
-for lib in $(ls bin/*.a); do
-    filename=$(basename $lib)
-    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.after
+for lib in bin/*.a; do
+    filename=$(basename "$lib")
+    arm-none-eabi-objdump -Cd "$lib" > "bin/${filename%.a}.after"
 done
 
-for cksum in $(ls bin/*.after); do
-    diff -u $cksum ${cksum%.after}.before
+for cksum in bin/*.after; do
+    diff -u "$cksum" "${cksum%.after}.before"
 done