userland: add assembly support

Move arm assembly cheat here, and start some work on x86 cheat as well.

userland/arch/x86_64/c/binutils_hack.c

@@ -0,0 +1,20 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#your-first-binutils-hack */
+
+#include <assert.h>
+#include <inttypes.h>
+
+int main(void) {
+#if 0
+	uint64_t in = 0xFFFFFFFF;
+	uint64_t out = 0;
+	__asm__ (
+		"mov %[in], %%rax;"
+		"myinc %%rax;"
+		"movq %%rax, %[out]"
+		: [out] "=g" (out)
+		: [in] "g" (in)
+		: "rax"
+	);
+	assert(out == in + 1);
+#endif
+}