scripts: fix shellcheck SC2046 warnings

Also:
- use more `--` end-of-options markers.
- checksrc.sh: use literal quotes.

Closes #1739

Makefile.am

@@ -50,7 +50,7 @@ DISTCLEANFILES += ChangeLog
 
 dist-hook:
 	rm -rf $(top_builddir)/tests/log
-	find $(distdir) -name "*.dist" -exec rm {} \;
+	find $(distdir) -name "*.dist" -exec rm -- {} \;
 	(distit=`find $(srcdir) -name "*.dist"`; \
 	for file in $$distit; do \
 	  strip=`echo $$file | sed -e s/^$(srcdir)// -e s/\.dist//`; \

ci/checksrc.sh

@@ -6,7 +6,7 @@ set -eu
 
 cd "$(dirname "$0")"/..
 
-git ls-files "*.[ch]" "*.cc" | xargs -n1 \
+git ls-files '*.[ch]' '*.cc' | xargs -n1 \
 ci/checksrc.pl -i4 -m79 -AFIXME -AERRNOVAR -AFOPENMODE -ATYPEDEFSTRUCT \
   -aaccept \
   -afclose \

ci/cmakelint.sh

@@ -57,4 +57,5 @@ cd "$(dirname "$0")"/..
     --max-branches 12 \
     --max-arguments 5 \
     --max-localvars 15 \
-    --max-statements 50
+    --max-statements 50 \
+    --

ci/shellcheck.sh

@@ -7,7 +7,7 @@ set -eu
 
 cd "$(dirname "$0")"/..
 
-# shellcheck disable=SC2046
+git grep -z -l -E '^#!(/usr/bin/env bash|/bin/sh|/bin/bash)' | xargs -0 -r \
 shellcheck --exclude=1091 \
   --enable=avoid-nullary-conditions,deprecate-which \
-  $(grep -l -E '^#!(/usr/bin/env bash|/bin/sh|/bin/bash)' $(git ls-files))
+  --

ci/spellcheck.sh

@@ -6,7 +6,8 @@ set -eu
 
 cd "$(dirname "$0")"/..
 
-# shellcheck disable=SC2046
-codespell --skip='docs/AUTHORS' \
-  --ignore-words='ci/codespell-ignore.words' \
-  $(git ls-files)
+git ls-files -z | xargs -0 -r \
+codespell \
+  --skip 'docs/AUTHORS' \
+  --ignore-words 'ci/codespell-ignore.words' \
+  --

maketgz

@@ -124,7 +124,7 @@ retar() {
   mkdir "$tempdir"
   cd "$tempdir"
   gzip -dc "../$targz" | tar -xf -
-  find libssh2-* -depth -exec touch -c -t "$filestamp" '{}' +
+  find libssh2-* -depth -exec touch -c -t "$filestamp" -- '{}' +
   tar --create --format=ustar --owner=0 --group=0 --numeric-owner --sort=name libssh2-* | gzip --best --no-name > out.tar.gz
   mv out.tar.gz ../
   cd ..