Build failure in new binutils

[Paul Goyette <paul%whooppee.com@localhost>]

With updated sources:

#    create  c++filt//build/netbsd-compat/src_ro/external/gpl3/binutils/usr.bin/c++filt/../../dist/binutils/doc/c++filt.1
/build/netbsd-compat/tools/x86_64/amd64/bin/nbsed -e "s/@PROGRAM@/c++filt/" < /build/netbsd-compat/src_ro/external/gpl3/binutils/usr.bin/c++filt/../../dist/binutils/doc/cxxfilt.man > /build/netbsd-compat/src_ro/external/gpl3/binutils/usr.bin/c++filt/../../dist/binutils/doc/c++filt.1
sh: cannot create /build/netbsd-compat/src_ro/external/gpl3/binutils/usr.bin/c++filt/../../dist/binutils/doc/c++filt.1: read-only file system
*** [c++filt.1] Error code 1


+--------------------+--------------------------+-----------------------+
| Paul Goyette       | PGP Key fingerprint:     | E-mail addresses:     |
| (Retired)          | FA29 0E3B 35AF E8AE 6651 | paul%whooppee.com@localhost     |
| Software Developer | 0786 F758 55DE 53BA 7731 | pgoyette%netbsd.org@localhost   |
+--------------------+--------------------------+-----------------------+