bsd.wrapper.mk and gawk 3.1.8

[Richard PALO <richard.palo%free.fr@localhost>]

apparently the native gawk package (3.1.8) on certain solaris systems 
have a problem with the following from bsd.wrapper.mk:
> # Filter to scrunch shell scripts by removing comments and empty lines.
> _WRAP_SH_CRUNCH_FILTER= ${AWK} ' \
>                 /^\#!/ { print } \
>                 /^[[:space:]]*\#/ || NF == 0 { next } \
>                 /.*/ { print } \
>                 '

Particular uncomfortable during a bootstrap, as it gives the following:
> ===> Extracting for bootstrap-mk-files-20130912
> ===> Patching for bootstrap-mk-files-20130912
> ===> Creating toolchain wrappers for bootstrap-mk-files-20130912
> gawk: fatal: Unmatched [ or [^: /^[[:space:]]*#/

confirmed with the quick test:
> richard@devzone:~$ cat ~/.profile |gawk ' \
> /^\#!/ { print } \
> /^[[:space:]]\#/ || NF == 0 { next } \
> /.*/ { print } \
> '
> gawk: cmd. line:3: fatal: Unmatched [ or [^: /^[[:space:]]\#/

which works with the pkgsrc gawk.

Is there not a means make this statement work with 3.1.8?