[libcxx][CI] Set Arm triples to match native clang build's default

[DavidSpickett]

Summary

We were using:
armv8-linux-gnueabihf
But for a native clang build the default target is:
armv8l-linux-gnueabihf

(ditto for v7)

Add the "l" to the target triples and update the one test
that is unsupported to look for the various possible names.

armv(7 or 8)(m or l, optionally)

The UNSUPPORTED does not include aarch64 because aarch64 Linux
(and others that follow Arm's AAPCS64) use quad precision for
long double where arm64 (darwin) does not:
https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms
https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#811arithmetic-types

[rovka]

I haven't had a chance to test this, but it seems sensible to me.

libcxx/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp

13–14

Should this also catch aarch64?

[DavidSpickett]

Explain why aarch64 is not listed in unsupported but arm64 is.

[DavidSpickett]

libcxx/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp

13–14

Surprised me too but no. arm64 darwin they have the same size but aarch64 Linux follows the AAPCS64 standard where they are different. (I assume BSD's do this too)

[DavidSpickett]

Arm specific CI stuff so landing without group approval.

libcxx/cmake/caches/Armv7Arm.cmake

 set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
-set(LIBCXX_TARGET_TRIPLE "armv7-linux-gnueabihf" CACHE STRING "")
+set(LIBCXX_TARGET_TRIPLE "armv7l-linux-gnueabihf" CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-marm" CACHE STRING "")
 set(CMAKE_C_FLAGS "-marm" CACHE STRING "")

libcxx/cmake/caches/Armv7Thumb-noexceptions.cmake

 set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
-set(LIBCXX_TARGET_TRIPLE "armv7-linux-gnueabihf" CACHE STRING "")
+set(LIBCXX_TARGET_TRIPLE "armv7l-linux-gnueabihf" CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-mthumb" CACHE STRING "")
 set(CMAKE_C_FLAGS "-mthumb" CACHE STRING "")
 set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")

libcxx/cmake/caches/Armv8Arm.cmake

 set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
-set(LIBCXX_TARGET_TRIPLE "armv8-linux-gnueabihf" CACHE STRING "")
+set(LIBCXX_TARGET_TRIPLE "armv8l-linux-gnueabihf" CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-marm" CACHE STRING "")
 set(CMAKE_C_FLAGS "-marm" CACHE STRING "")

libcxx/cmake/caches/Armv8Thumb-noexceptions.cmake

 set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
-set(LIBCXX_TARGET_TRIPLE "armv8-linux-gnueabihf" CACHE STRING "")
+set(LIBCXX_TARGET_TRIPLE "armv8l-linux-gnueabihf" CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-mthumb" CACHE STRING "")
 set(CMAKE_C_FLAGS "-mthumb" CACHE STRING "")
 set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")

libcxx/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 
 // The following platforms have sizeof(long double) == sizeof(double), so this test doesn't apply to them.
-// UNSUPPORTED: target={{arm64|armv8|armv7|armv7m|powerpc|powerpc64}}-{{.+}}
+// This test does apply to aarch64 where Arm's AAPCS64 is followed. There they are different sizes.
+// UNSUPPORTED: target={{arm64|armv(7|8)(l|m)?|powerpc|powerpc64}}-{{.+}}
 // UNSUPPORTED: target=x86_64-pc-windows-{{.+}}
 
 // <compare>
 
 // template<class T> constexpr strong_ordering strong_order(const T& a, const T& b);
 
 // libc++ does not support strong_order(long double, long double) quite yet.
 // This test verifies the error message we give for that case.