scripts: allow logging of commands with variables

In a lot of places, we need to call some commands with specific
variable settings, a-la:
var1=val1 var2=val2 /foo/bar/buz opt1 opt2

Unfortunately, we currently can not log the variable settings.

Enhance CT_DoExecLog with a crude heuristic that works pretty well
and that can also log setting variables.

Reported-by: ANDY KENNEDY <ANDY.KENNEDY@adtran.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.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