feat: detect march and mcpu

fix build on riscv64

tools/mfd_aes_brute/Makefile

@@ -5,15 +5,15 @@ MYCFLAGS = -Ofast
 MYDEFS =
 MYLDLIBS = -lcrypto
 
-# A better way would be to just try compiling with march and seeing if we succeed
-cpu_arch = $(shell uname -m)
-ifneq ($(findstring arm64, $(cpu_arch)), )
-    MYCFLAGS += -mcpu=native
-# iOS 'fun'
-else ifneq ($(findstring iP, $(cpu_arch)), )
-    MYCFLAGS += -mcpu=native
-else
+SUPPORT_MARCH := $(shell $(CC) -xc /dev/null -c -o /dev/null -march=native > /dev/null 2>/dev/null && echo y)
+SUPPORT_MCPU := $(shell $(CC) -xc /dev/null -c -o /dev/null -mcpu=native > /dev/null 2>/dev/null && echo y)
+
+ifeq ($(DONT_BUILD_NATIVE),y)
+    # do nothing
+else ifeq ($(SUPPORT_MARCH),y)
     MYCFLAGS += -march=native
+else ifeq ($(SUPPORT_MCPU),y)
+    MYCFLAGS += -mcpu=native
 endif
 
 ifneq ($(SKIPPTHREAD),1)
@@ -43,6 +43,8 @@ ifeq ($(USE_MACPORTS),1)
     MYLDFLAGS += -L$(MACPORTS_PREFIX)/lib/openssl-3 -L$(MACPORTS_PREFIX)/lib/openssl-1.1
 endif
 
+showinfo: $(info c flags: $(MYCFLAGS))
+
 brute_key : $(OBJDIR)/brute_key.o $(MYOBJS)
 
 mfd_aes_brute : $(OBJDIR)/mfd_aes_brute.o $(MYOBJS)