Fix escaping leading regex dashes in ./configure sources (#1152)

Fix escaping leading regex dashes in ./configure sources (#1152)

    grep: invalid option -- 't'
    Usage: grep [OPTION]... PATTERNS [FILE]...
    Try 'grep --help' for more information.

    Usage: grep [OPTION]... PATTERNS [FILE]...
    Try 'grep --help' for more information.
    ./configure: line 27524: test: too many arguments

    Usage: grep [OPTION]... PATTERNS [FILE]...
    Try 'grep --help' for more information.
    ./configure: line 27698: test: too many arguments

Configure scripts are written in m4, not shell. M4 treats [square
brackets] specially. We could use quadrigraphs instead (as documented in
autoconf manual) but `(-)` looks a lot simpler than `@<:@-@:>@`!