tree-wide: Add informal SHA256 checksum verification

for packages with custom `git checkout` command.

To avoid obvious mistakes.

%ci:no-build

packages/crypto-monitor/build.sh

@@ -32,4 +32,3 @@ termux_step_post_get_source() {
 termux_step_make_install() {
 	install -Dm700 -t $TERMUX_PREFIX/bin executable/crypto_monitor
 }
-