Enable coredumps from systemd units

On ARM, backtraces on C code are not terribly useful by default because
the stack cannot really be unwound, hence a custom compiler flag for
this. This has never been a problem because I've only ever debugged C++
code *on the device itself*, and for C++ code stack unwinding is enabled
by the language frontend because it's needed for exception support. On
the C code, not so much.

With this flag, U-Boot fails to build, but just its examples. There's no
need to help these examples in the first place, though, so let's just
screw^Wskip them.

I *think* I also need to explicitly enable non-zero core sizes, even if
I already have systemd-coredumpctl enabled via systemd magic.

Change-Id: I094c52c2ead9c1dd581de4974e9edd432c8b6894
diff --git a/board/czechlight/common/overlay/etc/systemd/system.conf b/board/czechlight/common/overlay/etc/systemd/system.conf
new file mode 100644
index 0000000..8f3e655
--- /dev/null
+++ b/board/czechlight/common/overlay/etc/systemd/system.conf
@@ -0,0 +1,72 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+#
+# Entries in this file show the compile time defaults.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
+#
+# See systemd-system.conf(5) for details.
+
+[Manager]
+#LogLevel=info
+#LogTarget=journal-or-kmsg
+#LogColor=yes
+#LogLocation=no
+#LogTime=no
+#DumpCore=yes
+#ShowStatus=yes
+#CrashChangeVT=no
+#CrashShell=no
+#CrashReboot=no
+#CtrlAltDelBurstAction=reboot-force
+#CPUAffinity=1 2
+#NUMAPolicy=default
+#NUMAMask=
+#RuntimeWatchdogSec=0
+#RebootWatchdogSec=10min
+#ShutdownWatchdogSec=10min
+#KExecWatchdogSec=0
+#WatchdogDevice=
+#CapabilityBoundingSet=
+#NoNewPrivileges=no
+#SystemCallArchitectures=
+#TimerSlackNSec=
+#StatusUnitFormat=description
+#DefaultTimerAccuracySec=1min
+#DefaultStandardOutput=journal
+#DefaultStandardError=inherit
+#DefaultTimeoutStartSec=90s
+#DefaultTimeoutStopSec=90s
+#DefaultTimeoutAbortSec=
+#DefaultRestartSec=100ms
+#DefaultStartLimitIntervalSec=10s
+#DefaultStartLimitBurst=5
+#DefaultEnvironment=
+#DefaultCPUAccounting=no
+#DefaultIOAccounting=no
+#DefaultIPAccounting=no
+#DefaultBlockIOAccounting=no
+#DefaultMemoryAccounting=yes
+#DefaultTasksAccounting=yes
+#DefaultTasksMax=15%
+#DefaultLimitCPU=
+#DefaultLimitFSIZE=
+#DefaultLimitDATA=
+#DefaultLimitSTACK=
+#DefaultLimitCORE=
+DefaultLimitCORE=infinity
+#DefaultLimitRSS=
+#DefaultLimitNOFILE=1024:524288
+#DefaultLimitAS=
+#DefaultLimitNPROC=
+#DefaultLimitMEMLOCK=
+#DefaultLimitLOCKS=
+#DefaultLimitSIGPENDING=
+#DefaultLimitMSGQUEUE=
+#DefaultLimitNICE=
+#DefaultLimitRTPRIO=
+#DefaultLimitRTTIME=