selftests: bpf: Add missing per-arch include path

[ Upstream commit 19090f0306f1748980596c6c71f1c4b128639cff ]

The prog_tests programs do not include the per-arch tools include
path, e.g. tools/arch/riscv/include. Some architectures depend those
files to build properly.

Include tools/arch/$(SUBARCH)/include in the selftests bpf build.

Fixes: 6d74d178fe ("tools: Add riscv barrier implementation")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240927131355.350918-2-bjorn@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/testing/selftests/bpf/Makefile

@@ -10,6 +10,7 @@ TOOLSDIR := $(abspath ../../..)
 LIBDIR := $(TOOLSDIR)/lib
 BPFDIR := $(LIBDIR)/bpf
 TOOLSINCDIR := $(TOOLSDIR)/include
+TOOLSARCHINCDIR := $(TOOLSDIR)/arch/$(SRCARCH)/include
 BPFTOOLDIR := $(TOOLSDIR)/bpf/bpftool
 APIDIR := $(TOOLSINCDIR)/uapi
 ifneq ($(O),)
@@ -44,7 +45,7 @@ CFLAGS += -g $(OPT_FLAGS) -rdynamic					\
 	  -Wall -Werror -fno-omit-frame-pointer				\
 	  $(GENFLAGS) $(SAN_CFLAGS) $(LIBELF_CFLAGS)			\
 	  -I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR)		\
-	  -I$(TOOLSINCDIR) -I$(APIDIR) -I$(OUTPUT)
+	  -I$(TOOLSINCDIR) -I$(TOOLSARCHINCDIR) -I$(APIDIR) -I$(OUTPUT)
 LDFLAGS += $(SAN_LDFLAGS)
 LDLIBS += $(LIBELF_LIBS) -lz -lrt -lpthread