Unable to build the AArch64 binutils sources with NDEBUG defined

[Nick Clifton <nickc@redhat.com>]

Hi Andrew,

   Sorry for picking on you with an AArch64 build problem,
   but you seem to active in the sources at the moment and
   this should not be a big issue to solve:

   If you build the AArch64 binutils sources with NDEBUG defined,
   the assert() function call becomes a no-op and this in turn
   leads to some compile time warnings about unused variables.
   Since we treat compile time warnings as errors, this means
   that the build fails.  For example:

   $ .../configure --quiet --target=aarch64-linux-gnu CFLAGS="-O2 -g -DNDEBUG"
   $ make all-binutils
   [...]
   opcodes/aarch64-asm.c: In function 'aarch64_ins_sve_strided_reglist':
   opcodes/aarch64-asm.c:1328:16: error: unused variable 'mask' [-Werror=unused-variable]

   There are a couple more like this.

   Fixing them is either a case of replacing the assert() with an "if () return <fail>"
   type statement, or marking the variable as possibly unused:

diff --git a/opcodes/aarch64-asm.c b/opcodes/aarch64-asm.c
index 565c4b10559..29e96e244bb 100644
--- a/opcodes/aarch64-asm.c
+++ b/opcodes/aarch64-asm.c
@@ -1325,7 +1325,7 @@ aarch64_ins_sve_strided_reglist (const aarch64_operand *self,
                                    ATTRIBUTE_UNUSED)
  {
    unsigned int num_regs = get_operand_specific_data (self);
-  unsigned int mask = 16 | (16 / num_regs - 1);
+  unsigned int mask ATTRIBUTE_UNUSED = 16 | (16 / num_regs - 1);
    unsigned int val = info->reglist.first_regno;
    assert ((val & mask) == val);
    insert_field (self->fields[0], code, val >> 4, 0);

   If you do not have the time to look into this issue, please let me know
   and I will fix the problems myself.

Cheers
   Nick