[flang] Relax the Bash version check

As per flang-compiler/f18-llvm-project#1344,
the `flang` bash script works fine with 4.4.19 and requiring
4.4.23 is too restrictive. Rather than keep updating the patch level,
this patch removes this particular check (so that it will only check the
major and minor versions instead).

As this is both rather straightforward and urgent, I'm merging this
without a review.

Author: banach-space

flang/tools/f18/flang

@@ -13,7 +13,7 @@
 #   * use the external compiler (defined via FLANG_FC environment variable) to
 #   compile the unparsed source files
 #
-# Tested with Bash 4.4.23. This script will exit immediately if you use an
+# Tested with Bash 4.4. This script will exit immediately if you use an
 # older version of Bash.
 #===------------------------------------------------------------------------===#
 set -euo pipefail
@@ -31,22 +31,17 @@ PRINT_VERSION="False"
 # === check_bash_version ======================================================
 #
 # Checks the Bash version that's used to run this script. Exits immediately if
-# it's lower than 4.4.23
+# it's lower than 4.4
 # =============================================================================
 check_bash_version() {
-  message="Error: Your Bash is too old. Please use Bash >= 4.4.23"
+  message="Error: Your Bash is too old. Please use Bash >= 4.4"
   # Major version
   [[ "${BASH_VERSINFO[0]:-0}" -lt 4 ]] && echo $message && exit 1
 
   # Minor version
   if [[ "${BASH_VERSINFO[0]}" == 4 ]]; then
     [[ "${BASH_VERSINFO[1]:-0}" -lt 4 ]] && echo $message && exit 1
   fi
-
-  # Patch version
-  if [[ "${BASH_VERSINFO[0]}" == 4 ]] && [[ "${BASH_VERSINFO[1]}" == 4 ]] ; then
-    [[ "${BASH_VERSINFO[2]:-0}" -lt 23 ]] && echo $message && exit 1
-  fi
 }
 
 # === parse_args ==============================================================