Disambiguate kernel-specific file names

This patch removes possible ambiguities with respect to the naming of
kernel-dependent binaries and libraries. It also removes the use of
kernel-specific global side effects from the build system. The reach of
kernel-specific peculiarities has thereby become limited to the actual
users of the respective 'syscall-<kernel>' libraries.

Kernel-specific build artifacts are no longer generated at magic places
within the build directory (like okl4's includes, or the L4 build
directories of L4/Fiasco and Fiasco.OC, or the build directories of
various kernels). Instead, such artifacts have been largely moved to the
libcache. E.g., the former '<build-dir>/l4/' build directory for the L4
build system resides at '<build-dir>/var/libcache/syscall-foc/build/'.
This way, the location is unique to the kernel. Note that various tools
are still generated somewhat arbitrarily under '<build-dir>/tool/' as
there is no proper formalism for building host tools yet.

As the result of this work, it has become possible to use a joint Genode
build directory that is usable with all kernels of a given hardware
platform. E.g., on x86_32, one can now seamlessly switch between linux,
nova, sel4, okl4, fiasco, foc, and pistachio without rebuilding any
components except for core, the kernel, the dynamic linker, and the timer
driver. At the current stage, such a build directory must still be
created manually. A change of the 'create_builddir' tool will follow to
make this feature easily available.

This patch also simplifies various 'run/boot_dir' plugins by removing
the option for an externally hosted kernel. This option remained unused
for many years now.

Issue #2190

repos/base-nova/etc/specs.conf

@@ -1,5 +1 @@
-#
-# Description of build platform
-#
-
-SPECS ?= genode nova_x86_32
+SPECS += genode nova vesa acpi pci ps2 framebuffer

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

@@ -6,7 +6,7 @@
 
 include $(BASE_DIR)/lib/mk/base-common.inc
 
-LIBS += startup
+LIBS += startup-nova
 
 SRC_CC += signal_submit.cc
 SRC_CC += thread.cc thread_myself.cc

repos/base-nova/lib/mk/spec/x86_32/core-nova.mk

@@ -0,0 +1,3 @@
+SRC_CC += spec/x86_32/pager.cc
+
+include $(REP_DIR)/lib/mk/core-nova.inc

repos/base-nova/lib/mk/spec/x86_32/core.mk

@@ -1,3 +0,0 @@
-SRC_CC += spec/x86_32/pager.cc
-
-include $(REP_DIR)/lib/mk/core.inc

repos/base-nova/lib/mk/spec/x86_32/startup-nova.mk

@@ -0,0 +1 @@
+include $(BASE_DIR)/lib/mk/spec/x86_32/startup.inc

repos/base-nova/lib/mk/spec/x86_64/core-nova.mk

@@ -0,0 +1,3 @@
+SRC_CC += spec/x86_64/pager.cc
+
+include $(REP_DIR)/lib/mk/core-nova.inc

repos/base-nova/lib/mk/spec/x86_64/core.mk

@@ -1,3 +0,0 @@
-SRC_CC += spec/x86_64/pager.cc
-
-include $(REP_DIR)/lib/mk/core.inc

repos/base-nova/lib/mk/spec/x86_64/startup-nova.mk

@@ -0,0 +1 @@
+include $(BASE_DIR)/lib/mk/spec/x86_64/startup.inc

repos/base-nova/mk/spec/nova.mk

@@ -1,14 +0,0 @@
-#
-# Specifics for the NOVA kernel API
-#
-
-SPECS += nova
-SPECS += pci ps2 vesa framebuffer
-
-#
-# We would normally have to do this only in the kernel lib. We do it in
-# general nonetheless to ensure that the kernel port, if missing, is added to
-# the missing-ports list of the first build stage. The kernel lib is evaluated
-# only at a later build stage.
-#
-NOVA_SRC_DIR := $(call select_from_ports,nova)/src/kernel/nova

repos/base-nova/mk/spec/nova_x86_32.mk

@@ -1,8 +1,4 @@
-#
-# Specifics for the NOVA kernel API x86 32 bit
-#
-
-SPECS += nova x86_32
+# \deprecated
 
+SPECS += x86_32
 include $(call select_from_repositories,mk/spec/x86_32.mk)
-include $(call select_from_repositories,mk/spec/nova.mk)

repos/base-nova/mk/spec/nova_x86_64.mk

@@ -1,8 +1,4 @@
-#
-# Specifics for the NOVA kernel API x86 64 bit
-#
-
-SPECS += nova x86_64
+# \deprecated
 
+SPECS += x86_64
 include $(call select_from_repositories,mk/spec/x86_64.mk)
-include $(call select_from_repositories,mk/spec/nova.mk)

repos/base-nova/src/core/nova/target.mk

@@ -0,0 +1,3 @@
+LIBS = core-nova
+
+include $(BASE_DIR)/src/core/target.inc

repos/base-nova/src/kernel/nova/target.mk

@@ -3,6 +3,7 @@ include $(call select_from_repositories,mk/spec/nova.mk)
 TARGET           = hypervisor
 REQUIRES         = x86 nova
 NOVA_BUILD_DIR   = $(BUILD_BASE_DIR)/kernel
+NOVA_SRC_DIR     = $(call select_from_ports,nova)/src/kernel/nova
 SRC_CC           = $(sort $(notdir $(wildcard $(NOVA_SRC_DIR)/src/*.cpp)))
 SRC_S            = $(sort $(notdir $(wildcard $(NOVA_SRC_DIR)/src/*.S)))
 INC_DIR          = $(NOVA_SRC_DIR)/include