add arch/generic include fallback to build rules

this sets the stage for the first phase of the bits deduplication.
bits headers which are identical for "most" archs will be moved to
arch/generic/bits.

Makefile

@@ -40,7 +40,7 @@ CFLAGS_AUTO = -Os -pipe
 CFLAGS_C99FSE = -std=c99 -ffreestanding -nostdinc 
 
 CFLAGS_ALL = $(CFLAGS_C99FSE)
-CFLAGS_ALL += -D_XOPEN_SOURCE=700 -I$(srcdir)/arch/$(ARCH) -Iobj/src/internal -I$(srcdir)/src/internal -Iobj/include -I$(srcdir)/include
+CFLAGS_ALL += -D_XOPEN_SOURCE=700 -I$(srcdir)/arch/$(ARCH) -I$(srcdir)/arch/generic -Iobj/src/internal -I$(srcdir)/src/internal -Iobj/include -I$(srcdir)/include
 CFLAGS_ALL += $(CPPFLAGS) $(CFLAGS_AUTO) $(CFLAGS)
 
 LDFLAGS_ALL = $(LDFLAGS_AUTO) $(LDFLAGS)
@@ -50,8 +50,9 @@ RANLIB  = $(CROSS_COMPILE)ranlib
 INSTALL = $(srcdir)/tools/install.sh
 
 ARCH_INCLUDES = $(wildcard $(srcdir)/arch/$(ARCH)/bits/*.h)
+GENERIC_INCLUDES = $(wildcard $(srcdir)/arch/generic/bits/*.h)
 INCLUDES = $(wildcard $(srcdir)/include/*.h $(srcdir)/include/*/*.h)
-ALL_INCLUDES = $(sort $(INCLUDES:$(srcdir)/%=%) $(GENH:obj/%=%) $(ARCH_INCLUDES:$(srcdir)/arch/$(ARCH)/%=include/%))
+ALL_INCLUDES = $(sort $(INCLUDES:$(srcdir)/%=%) $(GENH:obj/%=%) $(ARCH_INCLUDES:$(srcdir)/arch/$(ARCH)/%=include/%) $(GENERIC_INCLUDES:$(srcdir)/arch/generic/%=include/%))
 
 EMPTY_LIB_NAMES = m rt pthread crypt util xnet resolv dl
 EMPTY_LIBS = $(EMPTY_LIB_NAMES:%=lib/lib%.a)
@@ -202,6 +203,9 @@ $(DESTDIR)$(libdir)/%: lib/%
 $(DESTDIR)$(includedir)/bits/%: $(srcdir)/arch/$(ARCH)/bits/%
 	$(INSTALL) -D -m 644 $< $@
 
+$(DESTDIR)$(includedir)/bits/%: $(srcdir)/arch/generic/bits/%
+	$(INSTALL) -D -m 644 $< $@
+
 $(DESTDIR)$(includedir)/bits/%: obj/include/bits/%
 	$(INSTALL) -D -m 644 $< $@
 

configure

@@ -651,8 +651,9 @@ echo '#include <float.h>' > "$tmpc"
 echo '#if LDBL_MANT_DIG == 53' >> "$tmpc"
 echo 'typedef char ldcheck[9-(int)sizeof(long double)];' >> "$tmpc"
 echo '#endif' >> "$tmpc"
-if $CC $CFLAGS_C99FSE -I$srcdir/arch/$ARCH -I$srcdir/include $CPPFLAGS $CFLAGS \
-  -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
+if $CC $CFLAGS_C99FSE \
+  -I$srcdir/arch/$ARCH -I$srcdir/arch/generic -I$srcdir/include \
+  $CPPFLAGS $CFLAGS -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
 printf "yes\n"
 else
 printf "no\n"