build: support building all tools in a single binary

Add the --enable-single-binary option to the configure file.
When enabled, this option builds a single binary file containing
the selected tools.  Which tool gets executed depends on the value
of argv[0] which can be set implicitly through symlinks to the
single program.

This setup reduces significantly the size of a complete coreutils
install, since code from lib/libcoreutils.a is not duplicated in
every one of the more than 100 binaries.  Runtime overhead is
increased due to more dynamic libraries being loaded, and extra
initialization being performed for all utils.  Also initially
a larger binary is loaded from storage, though this is usually
alleviated due to caching and lazy mmaping of unused blocks,
and in fact the single binary should have better caching
characteristics.

Comparing the size of the individual versus single binary on x86_64:
  $ cd src
  $ size coreutils
  $ size -t $(../build-aux/gen-lists-of-programs.sh --list-progs |
              grep -Ev '(coreutils|libstdbuf)') | tail -n1
     text    data     bss     dec     hex filename
  1097416    5388   88432 1191236  122d44 src/coreutils
  4901010  124964  163768 5189742  4f306e (TOTALS)

Storage requirements are reduced similarly:
  $ cd src
  $ du -h coreutils
  $ du -ch $(../build-aux/gen-lists-of-programs.sh --list-progs |
             grep -Ev '(coreutils|libstdbuf)') | tail -n1
  1.2M    coreutils
  5.3M    total

When installing, the makefile will create either symlinks or
shebangs based on the --enable-single-binary setting, for
each configured tool. In this way, all the tools are still
callable individually, but they are all implemented by the same
"coreutils" binary installed on the same directory.

* .gitignore: Add new generated files.
* Makefile.am: New rules to generate build-aux/gen-single-binary.sh
  and install symlinks.
* NEWS: Mention the new feature.
* README: Add "coreutils" to the list of utils.
* bootstrap.conf: Regenerate src/single-binary.mk
* build-aux/gen-lists-of-programs.sh: New --list-progs option.
* build-aux/gen-single-binary.sh: Regenerate
* configure.ac: New --enable-single-binary option and other variables.
Disallow --enable-single-binary=symlinks with --program-prefix et. al.
* man/coreutils.x: Manpage hook.
* man/local.mk: Add manpage hook and fix dependencies.
* src/coreutils.c: Multicall implementation.
* src/local.mk: New rules for the single binary option.
* tests/local.mk: Add $single_binary_progs to support
require_built_() from init.cfg
* tests/misc/env.sh: Avoid the use of symlink to echo.
* tests/misc/help-version.sh: Add exception for coreutils.
* tests/install/basic-1.sh: Really avoid using ginstall strip
functionality if there is an issue with the independent strip command.
* src/kill.c: Changes to call exit() in main.
* src/readlink.c: Likewise.
* src/shuf.c: Likewise.
* src/timeout.c: Likewise.
* src/truncate.c: Likewise.

1 files changed, 9 insertions, 9 deletions

diff --git a/README b/README
index fa1a42966..bd0bce590 100644
--- a/README
+++ b/README
@@ -7,15 +7,15 @@ arbitrary limits.
 
 The programs that can be built with this package are:
 
-  [ arch base64 basename cat chcon chgrp chmod chown chroot cksum comm cp
-  csplit cut date dd df dir dircolors dirname du echo env expand expr
-  factor false fmt fold groups head hostid hostname id install join kill
-  link ln logname ls md5sum mkdir mkfifo mknod mktemp mv nice nl nohup
-  nproc numfmt od paste pathchk pinky pr printenv printf ptx pwd readlink
-  realpath rm rmdir runcon seq sha1sum sha224sum sha256sum sha384sum sha512sum
-  shred shuf sleep sort split stat stdbuf stty sum sync tac tail tee test
-  timeout touch tr true truncate tsort tty uname unexpand uniq unlink
-  uptime users vdir wc who whoami yes
+  [ arch base64 basename cat chcon chgrp chmod chown chroot cksum comm
+  coreutils cp csplit cut date dd df dir dircolors dirname du echo env
+  expand expr factor false fmt fold groups head hostid hostname id install
+  join kill link ln logname ls md5sum mkdir mkfifo mknod mktemp mv nice nl
+  nohup nproc numfmt od paste pathchk pinky pr printenv printf ptx pwd
+  readlink realpath rm rmdir runcon seq sha1sum sha224sum sha256sum sha384sum
+  sha512sum shred shuf sleep sort split stat stdbuf stty sum sync tac tail
+  tee test timeout touch tr true truncate tsort tty uname unexpand uniq
+  unlink uptime users vdir wc who whoami yes
 
 See the file NEWS for a list of major changes in the current release.