base: restructure signal-submit initialization

This patch allows core's 'Signal_transmitter' implementation to sidestep
the 'Env::Pd' interface and thereby adhere to a stricter layering within
core. The 'Signal_transmitter' now uses - on kernels that depend on it -
a dedicated (and fairly freestanding) RPC proxy mechanism for signal
deliver, instead of channeling signals through the 'Pd_session::submit'
RPC function.

repos/base-sel4/lib/mk/base-sel4-common.mk

@@ -8,7 +8,6 @@ include $(BASE_DIR)/lib/mk/base-common.inc
 
 LIBS += startup-sel4 syscall-sel4
 
-SRC_CC += signal_submit.cc
 SRC_CC += rpc_dispatch_loop.cc
 SRC_CC += thread.cc thread_myself.cc thread_bootstrap.cc
 SRC_CC += capability.cc capability_raw.cc

repos/base-sel4/lib/mk/base-sel4.mk

@@ -3,5 +3,6 @@ include $(BASE_DIR)/lib/mk/base.inc
 SRC_CC += capability_space.cc
 SRC_CC += thread_start.cc thread_init.cc
 SRC_CC += cache.cc
+SRC_CC += signal_transmitter.cc signal.cc
 
-LIBS += syscall-sel4 base-sel4-common timeout
+LIBS += syscall-sel4 base-sel4-common cxx timeout

repos/base-sel4/lib/mk/core-sel4.mk

@@ -26,6 +26,8 @@ SRC_CC      += \
                region_map_support.cc \
                irq_session_component.cc \
                signal_source_component.cc \
+               signal_transmitter_proxy.cc \
+               signal_receiver.cc \
                trace_session_component.cc \
                core_region_map.cc \
                core_mem_alloc.cc \
@@ -58,6 +60,8 @@ vpath io_mem_session_support.cc    $(GEN_CORE_DIR)
 vpath io_port_session_component.cc $(GEN_CORE_DIR)/spec/x86
 vpath platform_services.cc         $(GEN_CORE_DIR)/spec/x86
 vpath trace_session_component.cc   $(GEN_CORE_DIR)
+vpath signal_transmitter_proxy.cc  $(GEN_CORE_DIR)
+vpath signal_receiver.cc           $(GEN_CORE_DIR)
 vpath dataspace_component.cc       $(GEN_CORE_DIR)
 vpath core_mem_alloc.cc            $(GEN_CORE_DIR)
 vpath core_rpc_cap_alloc.cc        $(GEN_CORE_DIR)