Makefile: deeper folder nesting support; fail build when SCANINC fails

Code can now be placed in more deeply-nested directories.

Modified the SCANINC step of the build so that if SCANINC fails, the entire build fails on the spot.

Makefile

@@ -179,14 +179,14 @@ else
 endif
 
 ifeq ($(SCAN_DEPS),1)
-C_SRCS_IN := $(wildcard $(C_SUBDIR)/*.c $(C_SUBDIR)/*/*.c $(C_SUBDIR)/*/*/*.c)
+C_SRCS_IN := $(wildcard $(C_SUBDIR)/*.c $(C_SUBDIR)/*/*.c $(C_SUBDIR)/*/*/*.c $(C_SUBDIR)/*/*/*/*.c $(C_SUBDIR)/*/*/*/*/*.c)
 C_SRCS := $(foreach src,$(C_SRCS_IN),$(if $(findstring .inc.c,$(src)),,$(src)))
 C_OBJS := $(patsubst $(C_SUBDIR)/%.c,$(C_BUILDDIR)/%.o,$(C_SRCS))
 
 GFLIB_SRCS := $(wildcard $(GFLIB_SUBDIR)/*.c)
 GFLIB_OBJS := $(patsubst $(GFLIB_SUBDIR)/%.c,$(GFLIB_BUILDDIR)/%.o,$(GFLIB_SRCS))
 
-C_ASM_SRCS += $(wildcard $(C_SUBDIR)/*.s $(C_SUBDIR)/*/*.s $(C_SUBDIR)/*/*/*.s)
+C_ASM_SRCS += $(wildcard $(C_SUBDIR)/*.s $(C_SUBDIR)/*/*.s $(C_SUBDIR)/*/*/*.s $(C_SUBDIR)/*/*/*/*.s $(C_SUBDIR)/*/*/*/*/*.s)
 C_ASM_OBJS := $(patsubst $(C_SUBDIR)/%.s,$(C_BUILDDIR)/%.o,$(C_ASM_SRCS))
 
 ASM_SRCS := $(wildcard $(ASM_SUBDIR)/*.s)
@@ -280,7 +280,6 @@ include songs.mk
 $(CRY_SUBDIR)/%.bin: $(CRY_SUBDIR)/%.aif ; $(AIF) $< $@ --compress
 sound/%.bin: sound/%.aif ; $(AIF) $< $@
 
-
 ifeq ($(MODERN),0)
 $(C_BUILDDIR)/libc.o: CC1 := tools/agbcc/bin/old_agbcc$(EXE)
 $(C_BUILDDIR)/libc.o: CFLAGS := -O2
@@ -323,6 +322,12 @@ endif
 else
 define C_DEP
 $1: $2 $$(shell $(SCANINC) -I include -I tools/agbcc/include -I gflib $2)
+ifneq ($$(.SHELLSTATUS),0)
+	# Re-run the command here so its output is actually visible...
+	$$(shell $(SCANINC) -I include -I tools/agbcc/include -I gflib $2)
+	# ...and then fail with an error, within Make.
+	$$(error SCANINC failed with one or more FATAL ERRORS, which should have been printed somewhere above, during an attempted dependency scan of $2.)
+endif
 ifeq (,$$(KEEP_TEMPS))
 	@echo "$$(CC1) <flags> -o $$@ $$<"
 	@$$(CPP) $$(CPPFLAGS) $$< | $$(PREPROC) $$< charmap.txt -i | $$(CC1) $$(CFLAGS) -o - - | cat - <(echo -e ".text\n\t.align\t2, 0") | $$(AS) $$(ASFLAGS) -o $$@ -