Remove script usage of globstar, improving compatibility (#683)

CONTRIBUTING.md

@@ -20,7 +20,7 @@ and relies on similar information.
 For example, if implementing a lint that uses information about attributes,
 find other lints that check attribute information and use them as guides as you write your lint.
 
-Make sure to check the ["Development Environment"](#development-environment) section, especially if you are using Mac or Windows.
+Make sure to check the ["Development Environment"](#development-environment) section, especially if you are using Windows.
 
 The ["Adding a new lint"](#adding-a-new-lint) section of this document has a walkthrough for
 defining and testing new lints.
@@ -250,9 +250,7 @@ expected output files to include the new items, and you can get back on track.
 ## Development Environment
 
 While cargo-semver-checks is cross platform, the development task automation scripts in the scripts
-directory are not. In particular, a relatively modern `bash` (at least version 4.0) is required.
+directory require a `bash` shell to run.
 
-Linux users likely have bash 5+ already installed or available via their package manager.
 Windows users can get a bash + GNU command line environment via WSL or git bash.
-Mac users can install an updated bash via homebrew. The scripts will not work
-correctly using the default version of bash that comes with Mac OS.
+Linux and Mac OS typically have bash installed by default.

scripts/regenerate_test_rustdocs.sh

@@ -6,15 +6,15 @@ if [ -z "$BASH_VERSION" ]; then
     exit 1
 fi
 
-# have bash, check version
-if (( BASH_VERSINFO[0] < 4 )); then
-    >&2 printf 'This script requires bash version 4.0 or greater.\n'
-    exit 1
-fi
-
 # Fail on first error, on undefined variables, and on failures in pipelines.
 set -euo pipefail
 
+dir_is_newer_than_file() {
+    local dir="$1"
+    local file="$2"
+    [[ ! -e $file ]] || [[ $(find "$dir" -newer "$file" -exec sh -c 'printf found; kill "$PPID"' \;) ]]
+}
+
 export CARGO_TARGET_DIR=/tmp/test_crates
 RUSTDOC_OUTPUT_DIR="$CARGO_TARGET_DIR/doc"
 TOPLEVEL="$(git rev-parse --show-toplevel)"
@@ -32,19 +32,6 @@ echo "Generating rustdoc with: $(cargo $TOOLCHAIN --version)"
 RUSTDOC_CMD="cargo $TOOLCHAIN rustdoc"
 
 # Run rustdoc on test_crates/*/{new,old}/
-shopt -s globstar
-dir_is_newer_than_file() {
-    local dir=$1
-    local file=$2
-    local f
-    for f in "$dir"/**; do
-        if [[ $f -nt $file ]]; then
-            return 0
-        fi
-    done
-    return 1
-}
-
 if [[ $# -eq 0 ]]; then
     set -- "$TOPLEVEL/test_crates/"*/
     always_update=