bats/helpers: Create script before setting PATH

The following test case from `tests/new.bats` was failing on Windows
(using the MSYS2 Bash 4.3.46(2)-release from Git for Windows):

   ✗ new: error if setting permissions fails
     (from function `stub_program_in_path' in file lib/bats/helpers, line 320,
      in test file tests/new.bats, line 268)
       `stub_program_in_path 'chmod' 'printf "ARG: %s\n" "$@"' 'exit 1'' failed
     ARG: 700
     ARG: /tmp/test rootdir/bin/chmod
     ARG: -R
     ARG: u+rwx
     ARG: /tmp/test rootdir

Apparently on this platform, `chmod` wasn't already `hash`-ed, and using
`stub_program_in_path` to stub out `chmod` was causing
`create_bats_test_script` to look up `chmod` in `PATH` andinvoke the
stub script itself.

The fix: call `create_bats_test_script` before setting `PATH`. The
existing `stub_program_in_path for testing external program` test case
from `tests/bats-helpers.bats` now uses `chmod` for its example program
instead of `git`, which reproduced the original failure and verifies its
fix.

Author: mbland

lib/bats/helpers

@@ -313,11 +313,11 @@ stub_program_in_path() {
     in_process='true'
     shift
   fi
+  create_bats_test_script "${BATS_TEST_BINDIR#$BATS_TEST_ROOTDIR/}/$1" "${@:2}"
 
   if [[ ! "$PATH" =~ $bindir_pattern ]]; then
     export PATH="$BATS_TEST_BINDIR:$PATH"
   fi
-  create_bats_test_script "${BATS_TEST_BINDIR#$BATS_TEST_ROOTDIR/}/$1" "${@:2}"
 
   if [[ -n "$in_process" ]]; then
     hash "$1"

tests/bats-helpers.bats

@@ -240,11 +240,11 @@ __check_dirs_exist() {
   local bats_bindir_pattern="^${BATS_TEST_BINDIR}:"
   fail_if matches "$bats_bindir_pattern" "$PATH"
 
-  stub_program_in_path 'git' 'echo "$@"'
+  stub_program_in_path 'chmod' 'echo "$@"'
   assert_matches "$bats_bindir_pattern" "$PATH"
 
-  run git Hello, World!
-  assert_success 'Hello, World!'
+  run chmod ugo+rwx foo.txt
+  assert_success 'ugo+rwx foo.txt'
 }
 
 @test "$SUITE: {stub,restore}_program_in_path for testing in-process function" {