BUILD: tools: work around an internal compiler bug in gcc-3.4

BUILD: tools: work around an internal compiler bug in gcc-3.4

gcc-3.4 fails to compile standard.c :

src/standard.c: In function `str2sa_range':
src/standard.c:1034: error: unrecognizable insn:
(insn 582 581 583 37 src/standard.c:949 (set (reg/f:SI 262)
        (high:SI (const:SI (plus:SI (symbol_ref:SI ("*ss.4") [flags 0x22] <var_decl fe782e80 ss>)
                    (const_int 2 [0x2]))))) -1 (nil)
    (nil))
src/standard.c:1034: internal compiler error: in extract_insn, at recog.c:2083

The workaround is explained here :

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21613

It only requires creating a local variable containing the result of the
cast, which is totally harmless, so let's do it.