xbuild: Disable a few non-working arches

xbuild: Utility script to cross-compile static binaries

Version 0.5.1

dlog: Avoid trying to close an invalid file descriptor

Avoid a call to close() for the output file descriptor if the file has
not yet been opened. This can happen if no input at all is provided or
--skip-empty/-e is enabled and only empty lines are read.

The issue was reproducible as follows:

  % ./dlog -e < /dev/null
  WARN   Closing log: Bad file descriptor  [dlog.c:163, main]
  %

d[r]log: Reduce size of iovec struct arrays

Now that the trailing newline character is present in the line buffers
and not added anymore as the last iovec entry, it is possible to reduce
the size of the arrays by one.

d[sr]log: Add --skip-empty/-e command line option

Add a new --skip-empty/-e command line option which can be used to
discard empty input lines. By default empty input lines are copied
over to the output log.

Prevent logging from exiting on empty lines

Before this commit, `freadline` did not distinguish between an empty
line and EOF. This would case a printf such as

```
printf("\nHello, World\n");
```

to cause dlog, dslog, or drlog to exit.

In order to fix this, this commit includes the delimiter in the result
of `freaduntil`, which means `\n` will be included in all calls to
`freadline`.

Fixes #10
Fixes #12

Remove GCC 4.x -std=c99 workaround

Place #include <sys/sysinfo.h> in UCLIBC #ifdef

Compile under gcc 4.7 and with uclibc

Validated compilation under -std=gnu99 and -std=gnu11 using gcc 4.7.2
and gcc 9.3.0.

Add libsetunbuf LD_PRELOAD-able helper

man: Add COUNT metavariable for -m/--max-respawns

Also, regenerate the prebuilt dmon.8 file.

dmon: Propagate exit status of monitored process

This is particularly useful when using the -m/--max-respawns option to
know whether the monitored process finished correctly or otherwise know
that it failed after the maximum amount of retries.

Add max-respawns parameter to dmon

Version 0.5.0

Add .gitattributes to control archived files

Makefile: Add convenience "dist" target

Make git ignore libdmon.a

multicall: Support listing available applets

Add support for listing the available applets in a multicall dmon
binary, if the DMON_LIST_MULTICALL_APPLETS environment variable is
set. In that case only the list is printed, one item per line, and
the program will exit immediately.

README: Bring back text about MULTICALL=0|1