Makefile: Preprocess linker scripts and other general improvements

This patch started out as an attempt to run linker scripts through the
preprocessor. However, since that required some more infrastructure
changes, the build system is so intertwined, and there are so many other
small issues that turned up and are easier to fix (and get running, and
test thoroughly) in a single go, it turned out a little bigger. In order
of appearance, it:

- wraps direct linker invocations in a macro to avoid the widespread
  ifeq($(CONFIG_COMPILER_LLVM_CLANG),y) duplication.

- introduces an $(generic-deps) (equivalent to $(<class>-deps)) variable
  for targets that all files depend on

- makes the $(src-to-obj) function usable in multiple places as the
  authoritative way to get an output file name (even if the respective
  source file is also under build/), and makes it preserve extensions on
  everything except %.c and %.S (e.g. %.ld and %.asl)

- replaces the old $(<class>-postprocess) with a single
  $(postprocessors) variable. The old ramstage-postprocess was weird
  because it contained unescaped $(eval ...)s, meaning it gets executed
  as soon as the variable is first substituted (and the other
  $(eval ...) in the toplevel Makefile does essentially nothing). The
  new mechanism is just $(eval ...)ed directly after the recursive parse
  with no further magic. Files can freely append their own (escaped)
  content to it and access variables valid in the calling context (like
  $(<class>-objs)) directly.

- enhances the existing $(<class>-<type>-ccopts) mechanism with
  $(<class>-generic-ccopts) and $(generic-<type>-ccopts) to reduce
  duplication.

- makes .ld a type that can be added like a normal class file, causing
  it to be preprocessed with the correct #defines for the current class
  (needed for a follow-up feature). Migrates all linker scripts to this
  mechanism, which allows us to get rid of the weird $(ldoptions)
  mechanism (Kconfigs are replaced by preprocessor and no longer need to
  be defined as symbols).

- removes duplicate $(INCLUDES) from $(CFLAGS)

- repairs the crazy state of MIPS Makefiles, which seem to have been
  copied together from X86 despite having absolutely nothing in common
  with that architecture. They were using the same code to paste
  assembly pieces and linker scripts together without really needing it
  for anything, and even accidentally relied on a Kconfig default set
  in the arch/x86 subdirectory (I wish I was kidding). Changed them to
  work equivalent to the arm/arm64 Makefiles which are far closer
  related (also being SRAM-based platforms).

- moves the x86-specifc $(OPTION_TABLES_H) into the x86 Makefile.inc and
  fixes an rule that would've had an empty target if it wasn't defined

- removes the custom ldscript-gathering variables for x86 bootblock and
  romstage. The Makefile simply combines all .ld files that have been
  added to the respective class now.

- uses the normal class build system to replace some of the custom rules
  for autogenerated bootblock/crt0 files on x86, and removes some
  hardcoded flags by using the normal $(...-ccopts) variables.

- moves the handling of .asl files from the global Makefile.inc to x86.
  Changed to reuse the generic template for the preprocessing and C
  compilation steps.

- removed the extra <name>.o linking step before linking an rmodule for
  modules that don't require special linker flags (most of them).

- removes the incorrect assumption that there was a global $(LDFLAGS)
  from the SMM Makefile.inc (it was named $(LDFLAGFS in one place so it
  couldn't have been all that important ;) ).

- allow -j flag for parallel builds to be properly passed through to
  vboot child invocation by using special $(MAKE) variable.

BUG=None
TEST=Built for Falco, Nyan_Blaze, Stout, Rush_Ryu and Urara. Binary
diffed old and new coreboot.rom (and some manually uncompressed stages),
confirmed that images/stages are byte-for-byte identical except for some
embedded timestamps and commit hashes. (Addresses in Falco/Stout
ramstages shifting slightly due to different link order for ASL object
files within their directory. Some addresses in Urara ramstage .rodata
and some relocation entries in rmodules moved around due to linking them
in fewer steps.)

Change-Id: I50af7dacf616e0f8ff4c43f4acc679089ad7022b
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/219170
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/vendorcode/google/chromeos/Makefile.inc

@@ -66,7 +66,6 @@ INCLUDES += $(VB_INCLUDES)
 
 VBOOT_STUB_ELF = $(obj)/vendorcode/google/chromeos/vbootstub.elf
 VBOOT_STUB = $(VBOOT_STUB_ELF).rmod
-VBOOT_STUB_DOTO = $(VBOOT_STUB_ELF:.elf=.o)
 
 # Dependency for the vboot rmodules. Ordering matters.
 VBOOT_STUB_DEPS += $(obj)/vendorcode/google/chromeos/vboot_wrapper.rmodules_$(ARCH-ROMSTAGE-y).o
@@ -90,19 +89,16 @@ VBOOT_CFLAGS += $(patsubst -I%,-I$(top)/%,$(filter-out -include $(src)/include/k
 VBOOT_CFLAGS += -DVBOOT_DEBUG
 VBOOT_CFLAGS += $(rmodules_$(ARCH-ROMSTAGE-y)-c-ccopts)
 
-$(VBOOT_STUB_DOTO): $(VBOOT_STUB_DEPS)
-	$(CC_rmodules_$(ARCH-ROMSTAGE-y)) $(CFLAGS_rmodules_$(ARCH-ROMSTAGE-y)) $(LDFLAGS) -nostdlib -r -o $@ $^
-
 # Link the vbootstub module with a 64KiB-byte heap.
-$(eval $(call rmodule_link,$(VBOOT_STUB_ELF), $(VBOOT_STUB_DOTO), 0x10000,$(ARCH-ROMSTAGE-y)))
+$(eval $(call rmodule_link,$(VBOOT_STUB_ELF), $(VBOOT_STUB_DEPS), 0x10000,$(ARCH-ROMSTAGE-y)))
 
 # Build vboot library without the default includes from coreboot proper.
 $(VB_LIB):
 	@printf "    MAKE       $(subst $(obj)/,,$(@))\n"
 	$(Q)FIRMWARE_ARCH=$(VB_FIRMWARE_ARCH) \
 	CC="$(CC_romstage)" \
-		CFLAGS="$(VBOOT_CFLAGS)" \
-		make -C $(VB_SOURCE) \
+	CFLAGS="$(VBOOT_CFLAGS)" \
+	$(MAKE) -C $(VB_SOURCE) \
 		$(VBOOT_MAKEFLAGS) \
 		BUILD=$(top)/$(dir $(VB_LIB)) \
 		V=$(V) \
@@ -115,8 +111,7 @@ VB_SOURCE := vboot_reference
 INCLUDES += -I$(VB_SOURCE)/firmware/2lib/include
 INCLUDES += -I$(VB_SOURCE)/firmware/include
 
-verstage-c-ccopts += -D__PRE_RAM__ -D__VER_STAGE__
-verstage-S-ccopts += -D__PRE_RAM__ -D__VER_STAGE__
+verstage-generic-ccopts += -D__PRE_RAM__ -D__VER_STAGE__
 
 ifeq ($(CONFIG_RETURN_FROM_VERSTAGE),y)
 bootblock-y += verstub.c chromeos.c
@@ -134,12 +129,12 @@ VBOOT_CFLAGS += $(verstage-c-ccopts)
 VBOOT_CFLAGS += -include $(top)/src/include/kconfig.h -Wno-missing-prototypes
 VBOOT_CFLAGS += -DVBOOT_DEBUG
 
-$(VB2_LIB): $(obj)/config.h
+$(VB2_LIB): $$(generic-deps)
 	@printf "    MAKE       $(subst $(obj)/,,$(@))\n"
 	$(Q)FIRMWARE_ARCH=$(VB_FIRMWARE_ARCH) \
 	CC="$(CC_verstage)" \
-		CFLAGS="$(VBOOT_CFLAGS)" VBOOT2="y" \
-		make -C $(VB_SOURCE) \
+	CFLAGS="$(VBOOT_CFLAGS)" VBOOT2="y" \
+	$(MAKE) -C $(VB_SOURCE) \
 		BUILD=$(top)/$(dir $(VB2_LIB)) \
 		V=$(V) \
 		fwlib2
@@ -149,4 +144,4 @@ cbfs-files-y += $(call strip_quotes,$(CONFIG_CBFS_PREFIX))/verstage
 fallback/verstage-file = $(VERSTAGE_ELF)
 fallback/verstage-type = stage
 fallback/verstage-compression = none
-endif  # CONFIG_VBOOT2_VERIFY_FIRMWARE
+endif  # CONFIG_VBOOT2_VERIFY_FIRMWARE