complibs/cloog: create missing m4 dir

Because we now patch configure.in and configure, the Makefile quicks
in a re-build rule as the source files are now more recent than the
bundled generated files, and that fails because the m4 directory
is missing, although on some systems where aclocal is not installed,
the re-build rule does nothing (except a warning).

Always create tht directory.

Reported-by: Per Arnold Blaasmo <per-arnold.blaasmo@atmel.com>
[Also thanks to Thomas De Schampheleire <patrickdepinguin@gmail.com>
for some digging works on this issue]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 --- gcc-4.3.4/libffi/src/arm/sysv.S	

 +++ gcc-4.3.4/libffi/src/arm/sysv.S	

 @@ -235,7 +235,7 @@ ARM_FUNC_START ffi_closure_SYSV

  	stmfd	sp!, {ip, lr}

  	UNWIND .save	{r0, lr}

  	add	r2, sp, #8

 -	.pad #16

 +	UNWIND .pad #16

  	sub	sp, sp, #16

  	str	sp, [sp, #8]

  	add	r1, sp, #8