meson: replace bashism is POSIX shell compliant code (#463)

meson.build

@@ -222,15 +222,15 @@ install_subdir(
 # because configure_file strips the backslash in e.g. \@display,
 # resulting in @display, breaking our Perl code:
 # https://github.com/mesonbuild/meson/issues/7165
-bash = find_program('bash')
+sh = find_program('sh')
 replace_dirs = [
-  bash, '-c',  # Use bash to capture output and mark as executable
+  sh, '-c',  # Use bash to capture output and mark as executable
   'sed -e \'s,@abs_top_builddir@,'
   + meson.current_build_dir()
   + ',g;s,@abs_top_srcdir@,'
   + meson.current_source_dir()+',g\''
   # Only mark files ending in .pl as executables
-  + ' "$0" > "$1" && { [[ "${1##*.}" == pl ]] && chmod +x "$1" || true; }',
+  + ' "$0" > "$1" && { [ "${1##*.}" = pl ] && chmod +x "$1" || true; }',
   '@INPUT0@',   # $0
   '@OUTPUT0@',  # $1
 ]