Allow it to build on linux ARM cpu

When testing terra on a ubuntu ARM cpu it was not compiling due to a reference to non existing registers.
With this fix it can be compiled I've got this results for tests:
-----
=================
= passing tests
=================
eager.t
unstrict.t
incompletetypetest3.t
methodmissing.t
quoteenv.t
vecptr.t
requiretwice.t
simpleadd.t
addlanguage1.t
gctest.t
signext.t
overload.t
emptycalls.t
scope.t
lazycstring.t
strerror.t
simplerec.t
nestedcalls.t
quote2.t
methodsugar.t
recstruct2.t
staticmethod.t
fncalltest.t
arrayt2.t
emptystruct.t
cunion.t
recoverfromerror.t
ordercomplete.t
cast.t
macro2.t
incomplete.t
cbool.t
methodantiquote.t
overloadcall.t
examplelanguage1.t
bug3.t
offsetcalc.t
leaktest.t
template.t
anon.t
includetwice.t
splitprimary.t
objc2.t
overloadmethod.t
calc.t
incompletetypetest2.t
simplestruct.t
anonstruct2.t
lazylog.t
indexing64.t
overloadmethod2.t
dgemm2.t
antiquote1.t
lvaluequote.t
goto2.t
constructor.t
sugar.t
canon.t
ppnil.t
sumlanguage1.t
decltwice.t
objc.t
pattern.t
gemm.t
goto.t
shallowfreeze.t
overloadproduct.t
parsecrash.t
objtest.t
overload3.t
rename.t
overload2.t
ppltalk.t
emptytag.t
emptyname.t
sgemm3.t
incomplete4.t
quote8.t
lvaluetreelist.t
customtable.t
testrequire.t
struct.t
badname.t
structcast.t
fails/f1.t
fails/f16.t
fails/f24.t
fails/fnpointer.t
fails/f38.t
fails/overload.t
fails/missingmetamethod.t
fails/f30.t
fails/recursivecompile.t
fails/f23.t
fails/f7.t
fails/f37.t
fails/entrieserror.t
fails/recpattern.t
fails/intrinsic5.t
fails/let.t
fails/symbolvar6.t
fails/cast.t
fails/f43.t
fails/incomplete.t
fails/symbolvar7.t
fails/f14.t
fails/fnindex.t
fails/f22.t
fails/methodantiquote.t
fails/f34.t
fails/recursivecompile2.t
fails/f5.t
fails/attrstore.t
fails/abouttofreeze.t
fails/f10.t
fails/symboltest.t
fails/nilreturn.t
fails/recfn.t
fails/attrstore2.t
fails/f45.t
fails/missingmethod.t
fails/veclit.t
fails/failtrunc.t
fails/f21.t
fails/usercastwrong.t
fails/intrinsic1.t
fails/constructor.t
fails/attrload.t
fails/f4.t
fails/f29.t
fails/f18.t
fails/f8.t
fails/gettype.t
fails/f40.t
fails/dupvar.t
fails/overload3.t
fails/f3.t
fails/f46.t
fails/f12.t
fails/f19.t
fails/lvaluetreelist.t
fails/f28.t
fails/attrload2.t
fails/f31.t
fails/f13.t
fails/quoteescape2.t
fails/f35.t
fails/comparestruct.t
fails/f47.t
fails/opaque2.t
fails/veclit2.t
fails/f11.t
fails/f25.t
fails/ifelse.t
fails/opaque.t
fails/vectorerror.t
fails/intrinsic4.t
fails/symparam3.t
fails/niltype2.t
fails/quoteescape.t
fails/f44.t
fails/f39.t
fails/escapeerr.t
fails/getmethod.t
fails/intrinsic3.t
fails/macroselect.t
fails/veclit3.t
fails/arith.t
fails/escapemacro.t
fails/f2.t
fails/f9.t
fails/f36.t
fails/nesterror.t
fails/symbolvar3.t
fails/symbolvar.t
fails/overload4.t
fails/f41.t
fails/f0.t
fails/ifelse2.t
fails/f48.t
fails/f26.t
fails/f20.t
fails/f32.t
fails/f17.t
fails/intrinsic2.t
fails/f27.t
fails/symbolvar2.t
fails/symparam.t
fails/vectype.t
fails/f15.t
fails/f33.t
fails/nilsym.t
antiquote5.t
point.t
sgemmkernel.t
compilecallback.t
defaultoperator.t
dgemm3.t
structarg.t
nestnoerror.t
sumlanguage2.t
quote.t
abouttocompile.t
opaquealloc.t
lvaluepointer.t
falsespec.t
labelbug.t
niltype.t
macro3.t
method.t
forwardtodef.t
dgemm.t
symparam3.t
simpleapply.t
hexf.t
cnamespaces.t
bug.t
missingfields.t
antiquote4.t
getmethod.t
anonstruct.t
logical.t
macroselect.t
arrptr.t
receivercasts.t
testlang1.t
symparam2.t
f2.t
multimacro.t
zeroargs.t
varargcstring.t
proxystruct.t
testlang2.t
fib.t
macrolet.t
typeexp.t
symbolvar3.t
macrokey.t
cstruct2.t
foo.t
symbolvar.t
incomplete5.t
quote4.t
testlog.t
structrvalue.t
anon3.t
quoteblock.t
coverage.t
localenv2.t
indexingbug.t
cudatest.t
incompletetypetest.t
structconstructor.t
vecsize.t
methodrvalue.t
overloadmethod3.t
array.t
unm.t
vtablerec.t
pointerlike.t
conflict.t
blankexp.t
overloadrecv.t
crash1.t
incomplete2.t
alignment.t
crash2.t
empty.t
symbolvar2.t
luabridgerec.t
symparam.t
nonprototypec.t
def1.t
pratttest1.t
names.t
fact.t
tag.t
=================

=================
= FAILING tests
=================
painfulrecstruct.t
simplevec.t
class.t
fnpointer.t
benchmark_fannkuchredux.t
quote9.t
huge.t
aggregatearr.t
pretty.t
macro.t
speed.t
new.t
nolengthop.t
intrinsic.t
luabridge.t
interface2.t
isvolatile.t
blocking.t
hello.t
coverage3.t
bounce.t
pt.t
symbolvar4.t
usercast.t
nestextract.t
testdebug.t
nontemporal.t
symbolvar6.t
class3.t
antiquote3.t
or.t
blocking3.t
atoi.t
arraylit.t
symbolvar7.t
vecarith.t
stattest.t
vec.t
class6.t
sintable.t
ssimple.t
evenodd.t
quote3.t
clean.t
recfn.t
vars2.t
union.t
unpacktuple.t
globals.t
vars.t
hasbeenfrozen.t
benchmark_nbody.t
veclit.t
fib2.t
cnames.t
mathlib.t
shift.t
dgemmpaper.t
selectoverload.t
numliteral.t
fastcall.t
examplecompiler1.t
forbreak.t
gettype.t
quote5.t
localenv.t
call.t
quote7.t
terraluamethod.t
sgemm-old.t
cstruct.t
and.t
quoteselect.t
paren.t
diffuse.t
for.t
hello2.t
stencil.t
terranew.t
bug2.t
includec.t
simple.t
multiconstructor.t
ainline.t
printfarray.t
luabridgeunion.t
class5.t
rvaluerecv.t
renaming.t
blocking2-fixed.t
zeroreturn.t
nojit.t
string.t
ifelse.t
bf.t
exportdynamic.t
twolang.t
cunion2.t
let1.t
bug4.t
callbackcache.t
terralua.t
constant2.t
interface.t
arith.t
malloc.t
constant.t
expvec.t
forsym.t
coverage2.t
zeroreturn2.t
parsefail.t
cconv.t
symbolvar5.t
explicitcast.t
special.t
pthreads.t
fnptrc.t
avxhadd.t
printfloat.t
sgemm.t
gvarfault.t
torturechain.t
quote10.t
fakeasm.t
gcbug.t
antiquote2.t
pointerarith.t
class4.t
luabridge2.t
multiterra.t
luabridgefn.t
pow.t
recstruct.t
arrayt.t
completec.t
fnptr.t
quote6.t
luaterramethod.t
simpleglobal.t
incomplete3.t
let2.t
class2.t
cnamespace.t
blocking2.t
terracast.t
=================

277 tests passed. 146 tests failed.