Backtrace: system::exename not correct if in PATH

[ax3l]

The system::exename in AMReX, which is used for Backtrace generation on most systems, is not correct if the executable was started because it was found in PATH.

amrex/Src/Base/AMReX_BLBackTrace.cpp

Lines 208 to 222 in dbfa3b0

	have_eu_addr2line = file_exists("/usr/bin/eu-addr2line");
	if (have_eu_addr2line) {
	const pid_t pid = getpid();
	// cmd = "/usr/bin/eu-addr2line -C -f -i --pretty-print -p "
	eu_cmd = "/usr/bin/eu-addr2line -C -f -i -p "
	+ std::to_string(pid);
	}
	}
	std::string cmd;
	{
	have_addr2line = file_exists("/usr/bin/addr2line");
	if (have_addr2line) {
	cmd = "/usr/bin/addr2line -Cpfie " + amrex::system::exename;
	}
	}

This will result in errors of the kind

/usr/bin/addr2line: 'warpx': No such file

unless the tool eu-addr2line is found during backtrace generation.

Currently, using the more available addr2line tool, AMReX can only handle absolute paths or relative paths to the current working dir:

amrex/Src/Base/AMReX.cpp

Lines 357 to 361 in abc6696

	if (argv[0][0] != '/') {
	system::exename = FileSystem::CurrentPath();
	system::exename += "/";
	}
	system::exename += argv[0];