diagnostics: SARIF output: add "arguments" property (§3.20.2)

diagnostics: SARIF output: add "arguments" property (§3.20.2)

gcc/ChangeLog:
	* diagnostic-format-sarif.cc (sarif_invocation::sarif_invocation):
	Add "original_argv" param and use it to populate "arguments"
	property (§3.20.2).
	(sarif_builder::sarif_builder): Pass argv to m_invocation_obj's
	ctor.
	* diagnostic.cc (diagnostic_context::initialize): Initialize
	m_original_argv.
	(diagnostic_context::finish): Clean up m_original_argv.
	(diagnostic_context::set_original_argv): New.
	* diagnostic.h: Include "unique-argv.h".
	(diagnostic_context::set_original_argv): New decl.
	(diagnostic_context::get_original_argv): New decl.
	(diagnostic_context::m_original_argv): New field.
	* toplev.cc: Include "unique-argv.h".
	(general_init): Add "original_argv" param and move it to global_dc.
	(toplev::main): Stash a copy of the original argv before expansion,
	and pass it to general_init for use by SARIF output.
	* unique-argv.h: New file.

gcc/jit/ChangeLog:
	* jit-playback.cc (jit::playback_context::compile) Add a trailing
	null to argvec.

gcc/testsuite/ChangeLog:
	* c-c++-common/diagnostic-format-sarif-file-1.c: Verify that we
	have an "arguments" property (§3.20.2).

Signed-off-by: David Malcolm <dmalcolm@redhat.com>