lnt runtest test-suite: add --qemu-user-mode support

[kristof.beyls]

Summary

To make user more emulation with qemu work well, a specific cmake option
needs to be set when running the test suite under it.
This introduces the --qemu-user-mode option to make this straightforward
from a lnt runtest test-suite command line.

An example command line using this:

lnt runtest test-suite --sandbox lnt_sandbox \

--test-suite ~/dev/llvm.org/test-suite -j40 \
--qemu-user-mode=$HOME/dev/aarch64-emu/aarch64-qemu.sh \
--cppflags="-O3" \
--use-lit llvm-lit \
--cmake-define=CMAKE_TOOLCHAIN_FILE:FILEPATH=$HOME/dev/llvm.org/clang_aarch64_linux.cmake

Note that I haven't written regression tests yet for this - I thought I'd first ask for review on the general design before implementing tests.

[cmatthews]

Sure, this is fine. Can you add a test?

lnt/tests/test_suite.py

def run_test(self, opts):
         if not isexecfile(opts.lit):
             self._fatal("LIT tool not found (looked for %s)" % opts.lit)
         if opts.run_under:
             split = shlex.split(opts.run_under)
             split[0] = resolve_command_path(split[0])
             if not isexecfile(split[0]):
                 self._fatal("Run under wrapper not found (looked for %s)" %
                             opts.run_under)
+        if opts.qemu_user_mode and opts.run_under:
+            self._fatal("do not specify --run-under when using " +
+                        "--qemu-user-mode")
+        if opts.qemu_user_mode:
+            split = shlex.split(opts.qemu_user_mode)
+            split[0] = resolve_command_path(split[0])
+            if not isexecfile(split[0]):
+                self._fatal("Qemu user mode wrapper not found (looked for %s)" %
+                            opts.qemu_user_mode)
 
         if opts.single_result:
             # --single-result implies --only-test
             opts.only_test = opts.single_result
 
         if opts.only_test:
             # --only-test can either point to a particular test or a directory.
             # Therefore, test_suite_root + opts.only_test or
def _configure(self, path, extra_cmake_defs=[], execute=True):
             # Ensure that no flags get added based on build type when the user
             # explicitly specifies flags to use.
             for build_type in cmake_build_types:
                 defs['CMAKE_CXX_FLAGS_'+build_type] = ""
 
         if self.opts.run_under:
             defs['TEST_SUITE_RUN_UNDER'] = \
                 self._unix_quote_args(self.opts.run_under)
+        if self.opts.qemu_user_mode:
+            defs['TEST_SUITE_USER_MODE_EMULATION'] = '1'
+            defs['TEST_SUITE_RUN_UNDER'] = \
+                self._unix_quote_args(self.opts.qemu_user_mode)
         if self.opts.benchmarking_only:
             defs['TEST_SUITE_BENCHMARKING_ONLY'] = 'ON'
         if self.opts.only_compile:
             defs['TEST_SUITE_RUN_BENCHMARKS'] = 'Off'
         if self.opts.use_perf in ('time', 'all'):
             defs['TEST_SUITE_USE_PERF'] = 'ON'
         if self.opts.test_suite_externals:
             defs['TEST_SUITE_EXTERNALS_DIR'] = self.opts.test_suite_externals
@click.option("--use-perf", "use_perf",
                    "information or both",
               type=click.Choice(['none', 'time', 'profile', 'all']),
               default='none')
 @click.option("--perf-events", "perf_events",
               help=("Define which linux perf events to measure"),
               type=click.UNPROCESSED, default=None)
 @click.option("--run-under", "run_under", default="",
               help="Wrapper to run tests under", type=click.UNPROCESSED)
[e-mail]("--qemu-user-mode", "qemu_user_mode", default="",
+              help="Enable qemu user mode emulation using this qemu executable",
+              type=click.UNPROCESSED)
 @click.option("--exec-multisample", "exec_multisample",
               help="Accumulate execution test data from multiple runs",
               type=int, default=1, metavar="N")
 @click.option("--compile-multisample", "compile_multisample",
               help="Accumulate compile test data from multiple runs",
               type=int, default=1, metavar="N")
 @click.option("-d", "--diagnose", "diagnose",
               help="Produce a diagnostic report for a particular "