Disable RISCV_ATTRIBUTES Elf program header

This header is causing problems w/ SAIL, so for now just omit it.

isa/Makefile

@@ -58,7 +58,7 @@ vpath %.S $(src_dir)
 define compile_template
 
 $$($(1)_p_tests): $(1)-p-%: $(1)/%.S
-	$$(RISCV_GCC) $(2) $$(RISCV_GCC_OPTS) -I$(src_dir)/../env/p -I$(src_dir)/macros/scalar -T$(src_dir)/../env/p/link.ld $$< -o $$@
+	$$(RISCV_GCC) $(2) $$(RISCV_GCC_OPTS) -Wa,-mno-arch-attr -I$(src_dir)/../env/p -I$(src_dir)/macros/scalar -T$(src_dir)/../env/p/link.ld $$< -o $$@
 $(1)_tests += $$($(1)_p_tests)
 
 $$($(1)_v_tests): $(1)-v-%: $(1)/%.S