typo: call to _set_perm() is misspelled

[mwkrentel]

The function system_install() in xed_mbuild.py uses _set_perm() to set
the permissions of shared libraries to 755 (among other uses). But
when copying shared libraries (with --prefix), the call is misspelled
with 2 underscores on line 1818.

xed_mbuild.py:
1808 # copy the libraries
1809 libs = _gen_lib_names(env)
1810 if len(libs) == 0:
1811 xbc.cdie("No libraries found for install")
1812 for f in libs:
1813 mbuild.msgb("COPY", "{} <- {}".format(lib,f))
1814 if do_system_copy:
1815 mbuild.copy_file(f, lib)
1816 fn = mbuild.join(lib,os.path.basename(f))
1817 if env['shared']:
1818 __set_perm(fn)
1819 else:
1820 mbuild.make_read_only(fn)

As a result, './mfile.py --prefix=DIR --shared' fails with:

[STRIPPING] obj/libxed.so
[STRIP CMD] strip -x obj/libxed.so
[Making install dirs (if they do not exist)]
[MKDIR] /home/krentel/xed/prefix/include/xed
[MKDIR] /home/krentel/xed/prefix/lib
[COPY] /home/krentel/xed/prefix/lib <- obj/libxed.so
[COPY] /home/krentel/xed/prefix/lib <- obj/libxed.so
global name '__set_perm' is not defined

This code path only occurs when using both --prefix and --shared.
Curiously, this doesn't happen with 'install' target to make a kit.
Must be a different call to _set_perm().

Btw, both the caller and the callee of mbuild.copy_file() write a COPY
message, so all the COPY messages are written twice. You might want
to settle on one or the other.

--Mark

[markcharney]

pushed fixes. Let me know if you encounter any other issues. Thank you for reporting this!