autoconf-nativesdk: fix builds on fedora 17

autoconf-nativesdk: fix builds on fedora 17

Generally distros keep perl at /usr/bin/perl
Fedora 17 also has /bin/perl

this causes autoconf-nativesdk build on such distros to put perl
interpreter path in the perl scripts as /bin/perl

But we set perl location for target as /usr/bin/perl

This mismatch of perl path causes failure of rootfs image creation
like this:

| error: Failed dependencies:
|       /bin/perl is needed by autoconf-nativesdk-2.68-r6.x86_64.rpm
NOTE: package meta-toolchain-gmae-1.0-r7: task do_populate_sdk: Failed

The second sed command is for such a case:

eval 'case $# in 0) exec /bin/perl -S "$0";; *) exec /bin/perl -S "$0" "$@";; esac'

This line has two "/bin/perl" and we can't use a line number to tell
sed which line it is since the line numbers in different files are
defferent.

[YOCTO #2304]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>