[9fans] Plan9port file(1) fails to detect OS X binaries

[Aram Hăvărneanu]

P9p file(1) fails to recognise 64-bit Mach-O binaries (thus breaking
things like src(1) and friends). I don't know if it ever worked right.

: iridium:aram; uname -a
Darwin iridium 12.4.0 Darwin Kernel Version 12.4.0: Wed May 1
17:57:12 PDT 2013; root:xnu-2050.24.15~1/RELEASE_X86_64 x86_64
: iridium:aram;
: iridium:aram; gcc -v
Using built-in specs.
Target: i686-apple-darwin11
Configured with:
/private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/src/configure
--disable-checking --enable-werror
--prefix=/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2
--mandir=/share/man --enable-languages=c,objc,c++,obj-c++
--program-prefix=llvm-
--program-transform-name=/^[cg][^.-]*$/s/$/-4.2/
--with-slibdir=/usr/lib --build=i686-apple-darwin11
--enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/dst-llvmCore/Developer/usr/local
--program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11
--target=i686-apple-darwin11
--with-gxx-include-dir=/usr/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)
: iridium:aram;
: iridium:aram; which sam
/Users/aram/plan9/bin/sam
: iridium:aram;
: iridium:aram; 9 file /Users/aram/plan9/bin/sam
/Users/aram/plan9/bin/sam: as program
: iridium:aram; file /Users/aram/plan9/bin/sam
/Users/aram/plan9/bin/sam: Mach-O 64-bit executable x86_64
: iridium:aram;

--
Aram Hăvărneanu

[Anthony Sorace]

FWIW, file on Plan 9 knows about these well enough to at least
distinguish (386 | amd64 | 32-bit power) Mach-O executables.
The plan9 and p9p versions have diverged more than I'd have
expected, but it should be easy to import.
Anthony