complibs/cloog: fix linking with libm

In Ubuntu 11.04 and 11.10, the default options for ld have changed.
--no-copy-dt-needed-entries and --as-needed are now enabled by default, which
causes errors like:

[EXTRA] Checking CLooG/ppl
[DEBUG] ==> Executing: 'make' '-j3' '-s' 'check'
[ALL ] Making check in .
[ALL ] config.status: creating include/cloog/cloog-config.h
[ALL ] config.status: include/cloog/cloog-config.h is unchanged
[ALL ] libtool: link: i686-build_pc-linux-gnu-gcc -Wall -fomit-frame-pointer
-pipe -o cloog cloog.o -L/<snip>/build/static/lib ./.libs/libcloog.a -lm
/<snip>/build/static/lib/libppl_c.a /<snip>/build/static/lib/libpwl.a
/<snip>/build/static/lib/libppl.a /<snip>/build/static/lib/libgmpxx.a
/<snip>/build/static/lib/libgmp.a -lstdc++
[ALL ] /usr/bin/ld: /<snip>/build/static/lib/libppl.a(MIP_Problem.o):
undefined reference to symbol 'sqrt@@GLIBC_2.0'
[ALL ] /usr/bin/ld: note: 'sqrt@@GLIBC_2.0' is defined in DSO
/usr/lib/gcc/i686-linux-gnu/4.6.1/../../../i386-linux-gnu/libm.so so try adding
it to the linker command line
[ALL ] /usr/lib/gcc/i686-linux-gnu/4.6.1/../../../i386-linux-gnu/libm.so:
could not read symbols: Invalid operation
[ALL ] collect2: ld returned 1 exit status
[ERROR] make[2]: *** [cloog] Error 1
[ERROR] make[1]: *** [check-recursive] Error 1

See:
https://wiki.ubuntu.com/NattyNarwhal/ToolchainTransition

This patch fixes these errors by placing '-lm' at the right place on the command
line as libppl requires libm when linking cloog.

Signed-off-by: "Benoît Thébaudeau" <benoit.thebaudeau@advansee.com>

 http://bugs.gentoo.org/250342

 http://sources.redhat.com/bugzilla/show_bug.cgi?id=9685

 we cant assume sock_cloexec and pipe2 are bound together as the former defines

 are found in glibc only while the latter are a combo of kernel headers and

 glibc.  so if we do a runtime detection of SOCK_CLOEXEC, but pipe2() is a stub

 inside of glibc, we hit a problem.  for example:

 #include <grp.h>

 #include <stdio.h>

 main()

 {

 	getgrnam("portage");

 	if (!popen("ls", "r"))

 		perror("popen()");

 }

 getgrnam() will detect that the kernel supports SOCK_CLOEXEC and then set both

 __have_sock_cloexec and __have_pipe2 to true.  but if glibc was built against

 older kernel headers where __NR_pipe2 does not exist, glibc will have a ENOSYS

 stub for it.  so popen() will always fail as glibc assumes pipe2() works.

 diff -durN glibc-2.12.1.orig/socket/have_sock_cloexec.c glibc-2.12.1/socket/have_sock_cloexec.c

 --- glibc-2.12.1.orig/socket/have_sock_cloexec.c	2008-07-25 18:46:23.000000000 +0200

 +++ glibc-2.12.1/socket/have_sock_cloexec.c	2009-11-13 00:50:15.000000000 +0100

 @@ -16,9 +16,14 @@

     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA

     02111-1307 USA.  */

 +#include <fcntl.h>

  #include <sys/socket.h>

  #include <kernel-features.h>

  #if defined SOCK_CLOEXEC && !defined __ASSUME_SOCK_CLOEXEC

  int __have_sock_cloexec;

  #endif

 +

 +#if defined O_CLOEXEC && !defined __ASSUME_PIPE2

 +int __have_pipe2;

 +#endif