[ARM] ARM-specific attributes should be accepted for big-endian

[olista01]

Summary

The ARM-specific C attributes (currently just interrupt) need to check
for both the big- and little-endian versions of the triples, so that
they are accepted for both big and little endian targets.

TargetWindows and TargetMicrosoftCXXABI also only use the little-endian
triples, but this is correct as windows is not supported on big-endian
ARM targets (and this is asserted in lib/Basic/Targets.cpp).

[olista01]

Ping.

[rovka]

Looks like a sensible thing to do.

include/clang/Basic/Attr.td

 // Defines targets for target-specific attributes. The list of strings should
 // specify architectures for which the target applies, based off the ArchType
 // enumeration in Triple.h.
 class TargetArch<list<string> arches> {
   list<string> Arches = arches;
   list<string> OSes;
   list<string> CXXABIs;
 }
-def TargetARM : TargetArch<["arm", "thumb"]>;
+def TargetARM : TargetArch<["arm", "thumb", "armeb", "thumbeb"]>;
 def TargetMips : TargetArch<["mips", "mipsel"]>;
 def TargetMSP430 : TargetArch<["msp430"]>;
 def TargetX86 : TargetArch<["x86"]>;
 def TargetAnyX86 : TargetArch<["x86", "x86_64"]>;
 def TargetWindows : TargetArch<["x86", "x86_64", "arm", "thumb"]> {
   let OSes = ["Win32"];
 }
 def TargetMicrosoftCXXABI : TargetArch<["x86", "x86_64", "arm", "thumb"]> {

test/Sema/arm-interrupt-attr.c

 // RUN: %clang_cc1 %s -triple arm-apple-darwin -verify -fsyntax-only
+// RUN: %clang_cc1 %s -triple thumb-apple-darwin -verify -fsyntax-only
+// RUN: %clang_cc1 %s -triple armeb-none-eabi -verify -fsyntax-only
+// RUN: %clang_cc1 %s -triple thumbeb-none-eabi -verify -fsyntax-only
 
 __attribute__((interrupt(IRQ))) void foo() {} // expected-error {{'interrupt' attribute requires a string}}
 __attribute__((interrupt("irq"))) void foo1() {} // expected-warning {{'interrupt' attribute argument not supported: irq}}
 
 __attribute__((interrupt("IRQ", 1))) void foo2() {} // expected-error {{'interrupt' attribute takes no more than 1 argument}}
 
 __attribute__((interrupt("IRQ"))) void foo3() {}
 __attribute__((interrupt("FIQ"))) void foo4() {}
 __attribute__((interrupt("SWI"))) void foo5() {}
 __attribute__((interrupt("ABORT"))) void foo6() {}
 __attribute__((interrupt("UNDEF"))) void foo7() {}
 
 __attribute__((interrupt)) void foo8() {}
 __attribute__((interrupt())) void foo9() {}
 __attribute__((interrupt(""))) void foo10() {}