cbfstool: Fix build errors when building with clang

Now that we can set CC to an arbitrary compiler, fix issues that clang
finds. Luckily, there were only two trivial errors.

Change-Id: I0fd1f0f263a8ab7004f39cd36ed42d1a1cba5c04
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/5081
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

util/cbfstool/linux_trampoline.c

@@ -137,5 +137,5 @@ const unsigned char trampoline[] = {
 0x02, 0x09, 0x00, 0xf4, 0xeb, 0xfd
 };
 
-void * const trampoline_start = &trampoline;
+const void * const trampoline_start = &trampoline;
 const unsigned long trampoline_size = sizeof trampoline;

util/cbfstool/lzma/C/LzmaEnc.c

@@ -2080,7 +2080,7 @@ static void LzmaEnc_Finish(CLzmaEncHandle pp)
   if (p->mtMode)
     MatchFinderMt_ReleaseStream(&p->matchFinderMt);
   #else
-  pp = pp;
+  (void)pp;
   #endif
 }